25-cent Fan Mod

[IDSmoker]

25-cent Fan Mod

The 25-cent cost estimate is probably a bit high, since this is a pic of the only part you need:
http://myweb.cableone.net/sapen/FanMod/25-Cent%20Fan%20Mod%20-%20Required%20Part.jpg


The first step is to open the hood of your LX vehicle (this mod has only been confirmed to work on 2005 Magnum RTs, but should work on all other LXs) and then find and open the fuse box.

Once the fuse box is open you must remove correct part (I think it's called a relay) which you should find here:
http://myweb.cableone.net/sapen/FanMod/25-Cent%20Fan%20Mod%20-%20Fuse%20Box%20with%20Directions.JPG
(Sorry for the indecipherable writing, that's what I get for using MS PaintXP, but you should be able to figure it out.)


Now you simply plug in your high-cost replacement...
http://myweb.cableone.net/sapen/FanMod/25-Cent%20Fan%20Mod%20-%20Wire%20Installed.jpg

If you are still unsure, here's a close-up from another angle:
http://myweb.cableone.net/sapen/FanMod/25-Cent%20Fan%20Mod%20-%20Mod%20CloseUp.jpg


Congratulations, your fan should now be running!

Since the fan will continue to run until you remove the wire, and replace it with the relay you've hopefully saved, I definitely wouldn't leave it running overnight, but it didn't cause any battery problems during the several hours I used it at the dragstrip, and it did manage to lower engine temps a good 10-20 degrees!

If you are really ambitious you can certainly use a relay, switch, and lots of wire to rig a 'safer' more permanent fan switch, but since I'm not really planning to use it outside of the dragstrip, this is good enough for me.

Enjoy!

[GoofyGuy]

Oh boy it just hit me like a train for some reason. Go to autozone get a 180 degree fan wiring kit or an adjustable and just wire it into this spot. You can control the fans to come on earler for all you guys running a cooler thermo.

[jaak]

The mod outlined above forces one fan to high speed mode and disables the other fan for low speed mode, but still allows the FCM to enable it for high speed mode.

If you pull a different relay and put the jumper here, instead, you force both fans on, and the mode is controlled by the FCM. So they will go low speed, or high speed, as determined by the FCM, but never off.

http://i41.photobucket.com/albums/e266/srt8jaak/Fan%20Mod/Picture705.jpg

If you want both fans on high speed mode, then you must pull three relays and put in three jumpers as shown here. Make sure you use wire that can handle the current of the fan in high speed mode. (e.g. 12 gauge)

http://i41.photobucket.com/albums/e266/srt8jaak/Fan%20Mod/Picture706.jpg

It's a simple mod, just like the original outlined above, but requires three jumpers. The next step is to actually wire in a three position switch to do this from inside. Easy....

I apologise if I've driven this up over the 25 cent level...:mrgreen:

[ZMagnum]

I've jumpered the relay as shown in jaaks first picture. It works fine. Both fans are on low but I did get a CEL (0480) after I started up. I cleared it by pulling fuse 11 for a few mins. No big deal at all.

Edit - Fan codes you might see:
DTC P0480 Cooling Fan Relay 1 Control Circuit
DTC P0481 Cooling Fan Relay 2 Control Circuit
DTC P0482 Cooling Fan 3 Control Circuit Malfunction
DTC P0483 Cooling Fan Rationality Check Malfunction
DTC P0484 Cooling Fan Circuit Over Current
DTC P0485 Cooling Fan Power/Ground Circuit Malfunction

[jaak]

When Monitored:

With the ignition on. Battery voltage greater than 10 volts.

Set Condition:

An open or shorted circuit is detected in the radiator fan relay control circuit. One Trip Fault. Three good trips to turn off the MIL.





This is because the FCM monitors the relay coils to detect a fault. The first version of the modification, only removes one of two relays that are in parallel, so the FCM doesn't see an open or short, due to the other relays remaining in.

Of course, the best way to do this mod is to tie in external wiring to activate this, leaving the relays intact.

A second way is to measure the coil resistance and buy some resistors around that value to put in and satisfy the FCM by faking it out in to believing the relays are installed.

[Nightshade]

Leave the relays in, find some way to energize them externally..

I am thinking that because there is no diode across the coils that we can see, there must be one on the output of the circuit going to the coil.. that would prevent any back-voltage of we were to tap into the positive leg of the coil and dump 12V onto it... what's your take on this Jaak?

any way to energize the relay without pulling it out and rewiring it? I would hate to put 12V on the coil externally just to fry an output somewhere.. mind you most likely it wouldn't allow back-current..

hmmm..



When Monitored:

With the ignition on. Battery voltage greater than 10 volts.

Set Condition:

An open or shorted circuit is detected in the radiator fan relay control circuit. One Trip Fault. Three good trips to turn off the MIL.




This is because the FCM monitors the relay coils to detect a fault. The first version of the modification, only removes one of two relays that are in parallel, so the FCM doesn't see an open or short, due to the other relays remaining in.

Of course, the best way to do this mod is to tie in external wiring to activate this, leaving the relays intact.

A second way is to measure the coil resistance and buy some resistors around that value to put in and satisfy the FCM by faking it out in to believing the relays are installed.

[fnkychkn]

pretty sure FCM rad fan relay drivers control low side of relay coil.

[jaak]

Yes they do... While most of us think to switch the power, it's actually easier and more effective with electronics to switch the ground in and out.

The diode for dissappating back emf from the magnetic field in coil when it's turn off, may be built right in to the relay itself, or the FCM.

At first I thought a switch to ground to energise the relay would do it, but when I realised that the system looks to see if the relay is OK (short or open) it may see this as a fault as well. So whatever is done, the FCM has to be tricked into thinking all is well.

So it has to be determined how it measures it. There's two different states it can measure in. On or Off. And it's looking for two different conditions. Short or Open.

So how would it do any of these four different measurements? When the relay is powered on, there will be certain voltage drop seen at the FCM as well as current level. If there's an open, it will see no voltage or current. (relay pulled does this) If there's a short to ground on the power side (which seems to be the fault the service manual tests for) again, there would be no voltage or current. So one test would test for both conditions.

If it looks for a fault with the fan off, then it could be as simple as looking for a voltage on the controlling wire through the relay. An open relay = no voltage = fault. A shorted power to the relay = no voltage = fault.

Unfortunately, I won't be able to look at this as I'm getting on a plane to Chicago today. I hate it when work gets in the way of having fun!

Now one way to make this work, with the jumpers, is to make additional ones that will allow the FCM to still see the relay coils. A very short pair of jumpers with male and female spade connectors would allow the relay coil to be attached to the socket, but keep the relay out of the way so that the jumper to force the fan on, can still be inserted.

Or sacrifice relays by tearing them apart and hard wiring the switched side. Then you just pull the normal relay and insert the modded ones. Of course this drives the price way beyond 25 cents!

[ZMagnum]

I like this idea:

Now one way to make this work, with the jumpers, is to make additional ones that will allow the FCM to still see the relay coils. A very short pair of jumpers with male and female spade connectors would allow the relay coil to be attached to the socket, but keep the relay out of the way so that the jumper to force the fan on, can still be inserted.

[ZMagnum]

This works great. No CEL. A bit messy I admit. Wires could be shorter. Oh, well maybe next time.

http://members.cox.net/mmfrieden/topfan.jpg

http://members.cox.net/mmfrieden/topfanfront.jpg

http://members.cox.net/mmfrieden/closefan.jpg

[jaak]

Perfect, except you can lose the middle wire on the relay. You just need the two wires to make the FCM happy that it's seeing the coil. That's the normally closed contact, and since you're bypassing the normally open and the switched contacts, with the jumper, there's no point in bothering with the normally closed contact connection.

So, I'm curious, did you affect weather patterns, suck small animals, children and newspapers on to your grill?:)

[ZMagnum]

I was wondering about that middle wire. That will make it that much easier. Thanks.

Yes, I created my own dust devil.

Seriously, I went to McDonalds tonight with only the "both on low" fan mod w/no CEL. 76 degrees F outside. I noticed it took longer for the engine to reach full temp but it did eventually reach it. Next time I'll try both on high.

Perfect, except you can lose the middle wire on the relay. You just need the two wires to make the FCM happy that it's seeing the coil. That's the normally closed contact, and since you're bypassing the normally open and the switched contacts, with the jumper, there's no point in bothering with the normally closed contact connection.

So, I'm curious, did you affect weather patterns, suck small animals, children and newspapers on to your grill?:)

[Husker]

This is what we need to do for the folks who have the SC tuners and lower temp tstats. GSM is creating a "fan only" mod to help. but they are looking at 99 bucks for it. I think you guys should create a design and sell it for 25 bucks to cover your investment in time, materials etc...

Right now with the mod, my temps will swing from 183 driving to 205 or higher in traffic..

[DanRealtor]

Be careful leaving the fans on for any length of time. At our recent get together at Speedworld, several of us (myself included) got the dreaded click click, when trying to start our cars to drag race (dead battery). After a while the fans will run the battery down.

I used to do the .25 mod. Now I have the GSM Torque & Fan Mods. $199 for both. A convenient switch for the fan, and another for the Torque Management. The difference is huge as far as TM goes. Shift at 5900 in manual now without hitting the rev limiter, and all shifts in Drive or Auto Stick are noticeably firmer and quicker.

[HEMMISSEY]

now, did anyone make a switch to turn the fan on at high speed, instead of leaving it on constent high speed? I like the mod, (and I know that it will shut off when car is turned off) but just couldn't imagin my fans working hard 247?

[ZMagnum]

I've not made a switch. And BTW the fans run with this mod, even when the car is turned off. That's why there is a battery concern.

now, did anyone make a switch to turn the fan on at high speed, instead of leaving it on constent high speed? I like the mod, (and I know that it will shut off when car is turned off) but just couldn't imagin my fans working hard 247?

[jaak]

A better way to do this mod would be to have a temperature sensor that would make it run when you want it, even when the ignition is off. But not without a hood switch to defeat it when you pop the hood or it's taken in for service!

The original mod has one fan running on high. I'd like to see the results of both running on low, as that would suck less juice, and may have enough of the desired results. It has better fan coverage as well, on the rad. That would just be one jumper again, but on a different relay than the original mod.

http://i41.photobucket.com/albums/e266/srt8jaak/Picture705.jpg

If this mod cools just as effectively (and it's quite likely to, if not better) it will run longer and suck less power than the initial 25 cent mod. (And cost the same!)

[The_Bishop]

So, if I have this right, you can install a relay across the contacts shown here, and trigger the relay with a switched 12v source, and have the fans operate constantly when the key is in the 'on' position? Or, you could get even fancier and rig up a three-way switch to force the fans 'on' even when the ignition is off. I'd say this would be a lot more daily-driver friendly.

The mod outlined above forces one fan to high speed mode and disables the other fan for low speed mode, but still allows the FCM to enable it for high speed mode.

If you pull a different relay and put the jumper here, instead, you force both fans on, and the mode is controlled by the FCM. So they will go low speed, or high speed, as determined by the FCM, but never off.

http://i41.photobucket.com/albums/e266/srt8jaak/Picture705.jpg

[jaak]

You have to be careful. The FCM watches the relays. It wants to see 12 volts on the coil input, when not engaged. So you can do whatever you want, as long as you make the FCM think all is well. Otherwise it will throw a code and the check engine light will come on.

The jumpers are more for cooling while not running.

It's actually easy to insert one wire in the contact on the right, put the relay back in, and just ground the wire to force the fans on in low speed mode. But disconnect it before turning on the ignition or you'll get the check engine light on in about half a minute.

[JimTurner]

Check out the writeup in my sig below. "The one that i use" has a pretty detailed description about how the stock system works.

jimt

[jaak]

So does this thread further up.

It's really simple, actually.

[wquiles]

Check out the writeup in my sig below. "The one that i use" has a pretty detailed description about how the stock system works.

jimt
Nice job in the writeup :not_worth

Will

[lukeinva]

Anyone make a switch for this MOD yet??? I would like to do this but have the control to turn it off and on.

[RobAGD]

Luke - Look into the Jaak mod, I still have 1 extra I have all done up and tested ready for a switch and a little wire ;)

Extra Relay is $10ish at the dealer then you need to do a little mod magic to it.

-R

[lukeinva]

Thanks for the help rob!

[PowerWagon896]

Luke - Look into the Jaak mod, I still have 1 extra I have all done up and tested ready for a switch and a little wire ;)

Extra Relay is $10ish at the dealer then you need to do a little mod magic to it.

-R

Aren't the $2.50 Bosch relays the same?

[RobAGD]

No idea, When I started messing with this I got 6 Factory Relays to screw with. I killed 2 and made 4 working ones. If I were to get into this again for another batch, I would look into the Bosch relays, rumor has it they are a bit easier to mod as well.

-R

[PowerWagon896]

No idea, When I started messing with this I got 6 Factory Relays to screw with. I killed 2 and made 4 working ones. If I were to get into this again for another batch, I would look into the Bosch relays, rumor has it they are a bit easier to mod as well.

-R

I've used them (Bosch) on the Turner fan mod and they are true 5 pin relays. They can be used normally closed or normally open depending on which pin is used. (87/87A?)

[jaak]

You can use pretty well any of that style relay, as long as it has the resistor in it. I've put a resistor in a relay that didn't have it, and ran it for about 3 months with no issues.

For the OEM relay, I need to post pictures, but I've changed how I mod them now. I cut some card stock (like that business card the guy in the store force on you and you wanted to throw out immediately) and fit it in on the bottom as an insulator. I then bend one end of the diode lead in the shape of a U and slide it in under the coil from the opposite side of the coil terminals so the wire lead sits flat against the exposed terminal on the side. (Where the end of the resistor lead is sticking out.) and that gets soldered there.

The other end, I cut and bend at a 90 degree angle so it's parallel to the opening.

Now here's where it really gets easier than the other mod. Take a pair of needle nose pliers and grab the coil terminal with them, so the pliers are covering the length of the terminal. Twist it by rotating the pliers, back and forth like turning a key in a lock, locking and unlocking. 2-4 times and it snaps off, with the coil wire still attached.

Reposition it so it's next to the diode wire. Cut and strip the control wire. Solder all three together. Check for positioning, make sure you have no chance of it shorting against anything and if you want, test it, being careful with the wire so you don't pull it apart.

Once you're happy with it's operation, hot glue it together so those parts, the diode and the wire, can't move. Make sure you keep the glue away from the contacts and don't build it up too much on the side as the tabs inside the cover have to clear it.

I've found the tip on my iron is a good size for melting a hole in the relay cover and it's much more controllable than a drill. Just cleaning it is a pain after. So I make the hole then immediately clean the tip with a damp sponge to get the plastic off it.

Feed the wire through, slide the cover on, and you're ready to go.

[Token]

Nice

[Pale Rider]

Seriously, I went to McDonalds tonight with only the "both on low" fan mod w/no CEL.

Ok, help me out here guys. The above quote has me confused.
I'm interested in the simplest form of "both on low" fan mod w/no CEL.

Can I do jaak's FIRST picture, with the one jumper and get NO CEL? Or do I HAVE to do the relay hanging with wires?

[ZMagnum]

Ok, help me out here guys. The above quote has me confused.
I'm interested in the simplest form of "both on low" fan mod w/no CEL.

Can I do jaak's FIRST picture, with the one jumper and get NO CEL? Or do I HAVE to do the relay hanging with wires?

You can do any of the jumpers with the engine off and be okay. As soon as you start it up though you will get a code unless the computer is happy. It needs to see a resistance which tells it that the relay is there. My statement above refers to my jumpering the relay coils back on (positive and negative) and then jumpering across the relay switches.

The only acception to this is the high speed relay. You can jumper it and it puts the big fan on high w/out throwing codes. The high speed relay is not monitored by the computer.

[Pale Rider]

OK, so the very first post, showing just the one jumper, is ONE fan on high, and NO codes, right?

I'm only interested in this for the strip, so using a switch and all that isn't really what I'm after - just the simplest quickest way.

[MikeEast]

OK, so the very first post, showing just the one jumper, is ONE fan on high, and NO codes, right?

I'm only interested in this for the strip, so using a switch and all that isn't really what I'm after - just the simplest quickest way. That's what I do at the track, pop the relay, install the jumper and <ROAR> the big fan spins up hard and fast. No codes ever. I spaced off removing it after racing one night and drove home with it installed. Freaked me out when I pulled into the garage and shut down, only to hear the big fan still roaring away..

With my 170 thermostat (that's really more like a 180) I can stage with engine temp around 180-ish, climbing to 190+ at the big end of the track. If the lines are long and there is an appreciable wait, I'll run the motor every 10 minutes or so to move the coolant around. I've run it for 45 minutes or so without draining the battery as well.

Mike

[ZMagnum]

OK, so the very first post, showing just the one jumper, is ONE fan on high, and NO codes, right?

I'm only interested in this for the strip, so using a switch and all that isn't really what I'm after - just the simplest quickest way.

Yes. No codes. Just the one big fan on high.

You might want to consider this though. It's a really easy fan mod using the same relay w/no codes.
http://www.lxforums.com/board/showthread.php?t=46898

[Pale Rider]

Cool. Thanks to all of you for your info!

[jaak]

I like what someone else did, which was to buy another relay and hack it as a plug in.

You can fake out the PCM by putting a resistor jumper in as well. But whatever you do, never short the relay driver pin to 12 volts, or you will blow the lowside driver for the relay, in the FCM.

Which is why a modded relay is a good idea, 'cause you won't have a brain fart and plug the wrong wire in the wrong place.

[ZMagnum]

I like what someone else did, which was to buy another relay and hack it as a plug in.

You can fake out the PCM by putting a resistor jumper in as well. But whatever you do, never short the relay driver pin to 12 volts, or you will blow the lowside driver for the relay, in the FCM.

Which is why a modded relay is a good idea, 'cause you won't have a brain fart and plug the wrong wire in the wrong place.

I have a resistor jumper made up but I'm afraid to use it. What if the computer decides to power up that relay? Wouldn't it melt the resistor?

[jaak]

Nope, the current through the resistor is small... only around 20 mA if you're lucky, so the most power it will use is about a 1/4 of a watt.

[Pale Rider]

I just made this little pic, I'm leaving it in my car so I don't have to guess at the track.

http://i127.photobucket.com/albums/p156/7car7/Cars/Magnum%20Misc/25centfanmod-1.jpg

[jaak]

You can also add... The top picture will kill your battery faster than the bottom one, and does not draw air through both sides of the rad, just one.

[Pale Rider]

Definately! They both have advantages, not sure what's best!

So, if running with the Jaak mod, (with code) will that affect anything if code is ignored? I really don't want to have to scramble to throw the the relay back in when the line starts moving.

I'd just assume let the code sit there, 'till track session is done. But I wasn't sure if it would eventually go into limp home mode or something. That would be very embarassing at a track doing a 30 second 1/4 mile.

I'm going to try it on the way home from work, but I'd love to hear if there have been any issues with just letting it throw it's code for a whole day.

[jaak]

Well, the jaak mod is a modified relay and it won't throw codes... The 25 cent fan mod, will, but it will just register that it happened, not impact anything. You change a light bulb, it registers that too... You'd be surprised how many codes are likely in there already, that you never see!

The code just note's the event. It doesn't change the performance.

[SRT-8 Hemi]

Where can I purchase the relay wire?

[Deuuuce]

At Sears, when your lanes are racing, the staging area is stop and go. I just want to throw a switch while I'm sitting and idling, not while the motor is shut-off. Is that what the $200 switch kit is for from GS?

[Meister]

At Sears, when your lanes are racing, the staging area is stop and go. I just want to throw a switch while I'm sitting and idling, not while the motor is shut-off. Is that what the $200 switch kit is for from GS?In addition to providing one the means to completely disable ESP on the fly (no traction control, no torque management), the GSM Mod provides the ability to run a radiator fan whenever one chooses to do so.

[jaak]

Unfortunately, it's just one fan.

I'd go the NoESP route for both ESP and fans. WAAAAAAY Better than GSM's.

[Hal'sMag]

I've had the chance to play with fan mods, using the basic setups and thermo control.At 95+ ambient temps, need to go from 2 on low, or 1 on high, (same difference) to both low, then kick the big one on high to hold 180. Untill I shed some heat load, I'll use the 75 cent mod to keep from throwing a cel.Like FC stated, 100 below ambient is all the system will do, unless you go 2 on high, or add auxillary coolers to take load off the rad.I'm not going to run the crap out of my fans for normal driving.I've set my $40- thermo control mod to run at 200-204. Most of my driving is above 50 mph and keeps the temps below that, without fans. If I want to run hard, and I'll dial my temp down to 176 thermo setting.Everyone can do what they want, but this makes sence to me.With the 4127, on cool mornings, I need to pay attention to the EVIC.I had no problems with the 4128 running at 188, also see no difference in MPG with the 4127, but 1 MPG over stock 203, with the 4128.I used a jumper like the 75 cent mod to do the first relay in line for 2 on low. Found no difference from the 1 big one on high.Like you thought, need both on low, and the then the big one on high to keep the temps down.I'm npt daily racing , so will keep these settings until I race. JMO

[Meister]

Unfortunately, it's just one fan.

I'd go the NoESP route for both ESP and fans. WAAAAAAY Better than GSM's.Way better than GSM's fan mod portion of the GSM Mod.

Will need to read up on the ESP features of this cool new mod.

[sidetrack]

Has anyone with a CAI checked the Air Intake Temperature when the fans are running?

It would appear the extra fan action might stir up the hot air and force it into the CAI intake location.

Someone with Superchips could easily check the Air Intake Temperature with Data Acquisition, with and without the fans running.

[Hal'sMag]

My AFE stage2 definatley had no seal between the engine compartment. I opened the front to allow air in, and sealed to the engine bay about 90%. Bottom line is I now get little to no air from the engine bay.
I removed the IAT and taped over the opening in the manifold.
I found no difference in performance with the IAT in the heat of the rad., or in the cooler air inside the intake.

I've read on a post, that the IAT does little for performance, just at initial kickdown for point something seconds.
I would have pointed to the post, but ain't that good with the search features yet.

[Magmania]

What about your fan motor or bearings shortened life span?
Is that not a concern?

[Pale Rider]

What about your fan motor or bearings shortened life span?
Is that not a concern?

Are you reffering to the original post? Jumping the terminals to get the fan on? That was only meant for occasional use, as in Drag Racing. Not all the time.

[jaak]

Besides, I'd be happy to buy another fan... Unless you live somewhere hot all year, I don't see this as an issue. Half the year the fan's off, here.

[ajsince81]

I just made this little pic, I'm leaving it in my car so I don't have to guess at the track.

http://i127.photobucket.com/albums/p156/7car7/Cars/Magnum%20Misc/25centfanmod-1.jpg

Are these mods the same for the 300c SRT as shown above?

Also is it better to take them out before each run or leave them in all the time at the track?

Thanks for the good info.

[jaak]

Same for the 300C SRT (It's the same car, sorry, you didn't know?) and yes, put the relays back in when you start it.

Also, check out the fan mod from NoESP...

[Hal'sMag]

I did a couple thermo mods, and gained over 1 MPG.

I built a fan mod system with aftermarket temp probe, and it worked well when temperatures wrere moderate.

Now that the So.Cal heat has kicked in, it's pretty much worthless, unless I want to run both fans on high all the time.

Fans still don't address the heat sink on your intake system. Only shedding heat from the engine bay will do that.

Fans will not address the inadequacy of our cooling systems to cool our engines with stock rad., tranny cooler, oil cooler.

I think Meister and Matt are on the right track in increasing cooling capacity. Maybe heavy duty factory unit will do.

Meister has also removed the belly pan cover. More dust and dirt on the engine, but much more air flow through the engine bay + cooler intake temps. Just tie down the parts connected to what you remove.

Pale Rider makes some nice head covers that allow the heat trapped under the stock engine cover to dissapate.

Cool is Cool. And IMO adds the greatest $ for $ gain.

Just a daily driver - but still pulling 16+ and 25+ mpg.

Looking for a 300 for my wife. Any sugestions for the 6 vs. 5.7?

[Meister]

...I think Meister and Matt are on the right track in increasing cooling capacity. Maybe heavy duty factory unit will do.

Meister has also removed the belly pan cover. More dust and dirt on the engine, but much more air flow through the engine bay + cooler intake temps. Just tie down the parts connected to what you remove... (Blue emphasis mine.)
There you go guessing, Hal. :doh: :wink:

Actually, that's not the case at all. Airflow is in from the front fascia (giant manta ray maw, ala Xenon), the 300C Special Edition's egg crate grill, and my own ram air duct. This positive pressure has the engine compartment airflow flowing back and down over the engine and out through the now open area beneath the engine. If anything I get less dust & crud on my engine than when stock.

The only thing needing battened down after pulling the entire lower shroud assembly (2 pieces), BTW, is the fender well liners, which require a couple of stout zip ties to anchor them to the front bumper area to keep them off the front tires at elevated speeds.

[Pale Rider]

Are these mods the same for the 300c SRT as shown above? Good answer jaak!

Also is it better to take them out before each run or leave them in all the time at the track?

I did not take out the jumper at the track, in fact I've put it in for around town use every once in a while.

Here's one thing I've noticed, that I don't THINK has been mentioned.
When using the jumper in the position to have 2 fans on low, as soon as the motor is started, they (or maybe one, not sure) will go to HIGH speed when the check engine code comes on.

But keep in mind, this is not a code that only the dealer can reset. They will never see it. This code WILL be removed with 3 (or is it 4, can't recal) engine starts once the jumper is removed. Or you can do it with fuse 11. Either way, it is not storing a permanent code. I see no issue with keeping the jumper while driving.

But if you're nervous, just take it out when getting ready to start the motor - just be aware, the water is not circulating when engine is not running.

Thanks for the good info.

Mine in Red of course, (this line required to post).

[ajsince81]

Same for the 300C SRT (It's the same car, sorry, you didn't know?) and yes, put the relays back in when you start it.

Also, check out the fan mod from NoESP...


Thank You.

BTW, I'm aware of the fact that the MSRT8 is the same car with a different body. I saw that you drove a maggie after your posted this comment and thought this thread was mainly about the 300c (that was stated in the first post). I should of looked more closely.

[t500hps]

Made the wiring "harness" and went to install this mod in preperation of going to the track.....apparently the 08 models have a completely different fuse box. Can anyone tell me which piece to pull and install the wiring for this mod.....here's a pic.

[ZMagnum]

Made the wiring "harness" and went to install this mod in preperation of going to the track.....apparently the 08 models have a completely different fuse box. Can anyone tell me which piece to pull and install the wiring for this mod.....here's a pic.

For the 25 cent fan mod that turns the big fan on high? Let me go check. I'll be back in a minute.

[t500hps]

.......oops

[ZMagnum]

OK, of the cluster of 3 you pull the relay in the corner and you jumper it left to right not front to back like you do with the pre-2008 models.

[t500hps]

OK, of the cluster of 3 you pull the relay in the corner and you jumper it left to right not front to back like you do with the pre-2008 models.

OK...you mean this relay and these 2 contact points (#21 on the inside of the cover)

EDIT....deleted the pic since it was wrong.

[ZMagnum]

No the one to the right of it. Same jumper contact points.

[t500hps]

Like this??? took new pics for anyone checking this thread looking for info on 08 models.

I have another question about resetting the adaptives for the transmission. See below the wire the fuse marked with a little silver marker (middle one). Is that the fuse you pull to reset the adaptives?

[ZMagnum]

Like this??? took new pics for anyone checking this thread.

I have another question about resetting the adaptives for the transmission. See below the wire the fuse marked with a little silver marker (middle one). Is that the fuse you pull to reset the adaptives?

Yes. That's the correct fan relay and that's the correct fuse to reset the adaptives. I marked mine as well.

[330toSRT8]

Ok, I have a question. For the longest time I had the fans wired as you can see in this photo:
http://arvizo.net/images/SRT8FanModFusebox.jpg

This configuration allows me to turn the upper fan on high when I flip the switch. Based on what I read above, using this relay prevents the lower fan from turning on in low speed, but will still go high when the computer tells it to. In this configuration, when I have the switch off and the AC off I do not hear or see the fans kick on until the temp is well above 200.

After reading Jaak's first post, I decided to try the other relay so that my switch would turn both fans on low. Flipping the switch on does indeed turn both fans on low. The problem is when the switch is off I still hear and see the upper fan going into low speed even though the temp is well below the stock thermostat. Here's an example. My car was already warm from driving earlier. I turned the car on and the water temp showed 179. The switch was off. For the first five seconds both fans were off, but then the upper fan turned on low. The AC was off as well. Why should any fan kick on when the water temp is only 179-181 with the AC off?

I prefer to be able to turn both fans on low rather than just one fan on high, but I don't want any fans running when I have the AC off and the water temp is still below my thermostat temp. BTW, I'm running a 180 Motorad thermostat. Thanks for any help.

[JimTurner]

Ok, I have a question. For the longest time I had the fans wired as you can see in this photo:
http://arvizo.net/images/SRT8FanModFusebox.jpg

This configuration allows me to turn the upper fan on high when I flip the switch. Based on what I read above, using this relay prevents the lower fan from turning on in low speed, but will still go high when the computer tells it to. In this configuration, when I have the switch off and the AC off I do not hear or see the fans kick on until the temp is well above 200.

After reading Jaak's first post, I decided to try the other relay so that my switch would turn both fans on low. Flipping the switch on does indeed turn both fans on low. The problem is when the switch is off I still hear and see the upper fan going into low speed even though the temp is well below the stock thermostat. Here's an example. My car was already warm from driving earlier. I turned the car on and the water temp showed 179. The switch was off. For the first five seconds both fans were off, but then the upper fan turned on low. The AC was off as well. Why should any fan kick on when the water temp is only 179-181 with the AC off?

I prefer to be able to turn both fans on low rather than just one fan on high, but I don't want any fans running when I have the AC off and the water temp is still below my thermostat temp. BTW, I'm running a 180 Motorad thermostat. Thanks for any help.


Look at the instructions for my fan mod in my sig. You may not want to do the mod, but I have detailed instructions about how the stock fan controls are wired. Essentially, both fans on "low" are running in series with 12v in on one side of a fan, 2 fan wires connected and the fourth to ground. Two fans on high have 12v across each fan independently. The third relay dictates whether the fans run in series or parallel.

HTH

jimt

[330toSRT8]

Look at the instructions for my fan mod in my sig. You may not want to do the mod, but I have detailed instructions about how the stock fan controls are wired. Essentially, both fans on "low" are running in series with 12v in on one side of a fan, 2 fan wires connected and the fourth to ground. Two fans on high have 12v across each fan independently. The third relay dictates whether the fans run in series or parallel.

HTH

jimt
Ok, I'm pretty sure I'm doing what you describe in the writeup. Here is my wiring diagram from when it was set for one fan on high.
http://arvizo.net/images/FanMod2.JPG

Now it is wired the same except I'm using relay #40 instead of #39. But the upper fan kicks in five seconds after I turn on the car regardless of the water temp.

[Junior]

Anyone know what might be wrong if the 25c mod does NOT turn the fans on? We tried it on each of the two relay sockets closest to the jump point, and nothing. Also confirmed the jump wire itself did work on another car, but on this particular car (300C SRT), it does not turn anything on. It has in the past. The fans do come on normally while driving (you can hear 'em come on and turn off).

Any ideas?

[jaak]

The problem is when the switch is off I still hear and see the upper fan going into low speed even though the temp is well below the stock thermostat.

You can't have one fan running on low, as it takes both wired in series to allow them to run in low. However, if you accidentally shorted out the driver to B+, you will cook it in the FCM and your fans will never turn off.

The only way to fix that is to buy a new FCM (Which is easier than repairing one).

Double check that you truly have one fan running on low. If you do, you're wired something up weird.

Junior, I don't know that I have an answer for you, but when was that car built? There are some variations in the fan circuits. For example, Hemiwagn and my SRT8 Magnums, both have an extra relay mounted on the back of where the fans are. I've never seen it identified in the service manual. His Charger, same model year, but later build date, doesn't have that relay. I seem to remember Jeremy's (PPP) stock '05 300C SRT8 also had the extra relay. (He was kind enough to let me drive it while they did the cam swap on my car.)

[Junior]

Junior, I don't know that I have an answer for you, but when was that car built?
Thanks jaak - June '05 build.

There are some variations in the fan circuits. For example, Hemiwagn and my SRT8 Magnums, both have an extra relay mounted on the back of where the fans are. I've never seen it identified in the service manual. His Charger, same model year, but later build date, doesn't have that relay. I seem to remember Jeremy's (PPP) stock '05 300C SRT8 also had the extra relay. (He was kind enough to let me drive it while they did the cam swap on my car.)
Are you thinking that particular relay (if she has it) may have failed? I'll go take a look tomorrow and see if we can find the one you mean.

[SilverSRTSedan]

..

[08 stoned charger]

Yes. That's the correct fan relay and that's the correct fuse to reset the adaptives. I marked mine as well.

Is there a low fan speed mod for the 08? I think the high speed mod is to fast and the battery will drain much faster.

[ZMagnum]

Is there a low fan speed mod for the 08? I think the high speed mod is to fast and the battery will drain much faster.

The 3 fan relays are together in the 08's. They serve the same purpose as previous model years but are oriented differently. There is a relay you can jumper that will put both fans on low but you will get a CEL unless you do one of the more involved fan mods. The computer needs to see resistance provided by the relay.

The best thing to do is get a Predator tuner and adjust the fan turn on temps.

[08 stoned charger]

The 3 fan relays are together in the 08's. They serve the same purpose as previous model years but are oriented differently. There is a relay you can jumper that will put both fans on low but you will get a CEL unless you do one of the more involved fan mods. The computer needs to see resistance provided by the relay.

The best thing to do is get a Predator tuner and adjust the fan turn on temps.
I have a Predator but I'm thinking of cooling down at the track. Which relay turns both fans on low speed? Is it safe to drive with the wire in place?
Thanks

[ZMagnum]

I have a Predator but I'm thinking of cooling down at the track. Which relay turns both fans on low speed? Is it safe to drive with the wire in place?
Thanks

I've not done this on my 08 so I don't know. You can remove the 3 relays one at a time and try jumpering until you get both fans on low. Just make sure you jumper the relay switch and not the postive and negative sides that suppies power to the relay.

It is safe to drive with it in place but you will get the CEL.

BTW, I've found that idling my engine in the lanes with the fan running from the Predator settings gives a lower engine coolant temp then turning the engine off and running the fans with the hood up. The difference is the coolant is circulating with the engine running vs. no circulation of coolant with the engine off. I'm running the 170 degree t-stat.

[08 stoned charger]

:beerchug:You Da Man!
Thanks for all your help!

[RTRT57]

I have an 08' Charger Hemi. My fuse box looks different than the examples shown. Which relay should I remove to install the jumper?

Thanks!

[RTRT57]

Disregard previous reply. I should have read all the pages before posting my question. I hate when that happens!