The $40, Temp-Sensing Fan Mod

[95ttoplt1]

Hey guys after looking at the fan mods here and taking some hints, I came up with my own design. I didn't like the idea of having to manualy turn them on and off. I'm lazy.

I tested this on my SRT-8, with 180 T-stat, the highest temps I saw, were 190 at the end of a WOT blast, within 1/8 mile the temps were right back to 183.

I have mine set fully counter clock wise, and they come one by themselves at 180, key on or off.

Tools needed:
13mm socket and ratchet
Electrical crimp pliers
Soldering iron
Solder
Small flat blade screw driver
Drill and 3/8 bit
Something to cut metal bracket(tin snips, hacksaw ect..)

Total cost is around 40 dollars, the only thing you need is the kit I listed and a extra relay(optional, you can use the stock relay.


Anyway I found this little control at Summit for 24.99 plus 10 bucks handling.

Its made by Flex-a-lite and is partnumber 31147







Here is what comes in the kit.



There is a length of wire, 2 spade connectors, 1 ring connector, 3 sheet metal scews, 2 machine screws, 2 flat washers, insulated cover, temp control, bracket, butt connector, knob for temp control.

The first order of bussiness is to modify the bracket for use on our cars. For this we need to cut off the side with the three small holes. Shown here.



Next you need to drill a 3/8 hole into this vertical part where the pen is pointing, as close to the top as you can, within reason.



Then you can mount the bracket, I used the passenger side hood latch bolt to mount this. It stays very hidden and is easily accessed to do adjustments.

You can get to this bolt by removing the two plastic trim pieces in front of the core support. I pulled mine up from the ends like this.





This gives you access to this bolt, which we will mount the backet to.



Remove this bolt with a 13mm socket and ratchet., Then insert the bolt into the bracket like so.



Then install the bolt into its original hole. Like so.




Next mount up the temp control. Starting with the rear screw.




Then you can run the temp probe. There are 2 ways to do this. You can insert it into the fins of the radiator(like I did) or you can losen a hose clamp and slide the temp probe between the hose and radiator neck. Just be sure not to kink the probes wire. Here is how I mounted mine. It is mounted next to the inlet to the radiator. It was hard to get in but it is crucial to get in as far as you can. Mine is about 1/4 farther in than in this picture.




Next we start the wiring.

We will need to modify or replace the gray relay shown here, notice the stock relays are black



I used a version of the Jaaked Relay found here http://ca.geocities.com/srt8_@rogers.com/main.htm

But instead of the factory relay I used a Bosch relay pictured here



I actually broke my stocker so I looked for something easier and these are the ticket. I shake too bad to solder fine parts, these bosch relays were easier to solder as the parts we bigger,the parts that needed to be soldered are a bit more sustantial as well.

You can follow the directions Jaak gives to remove the cover on the relay. The bosch are easier to disassemble than the stockers as well. Make sure to mark the cover before removing, it will only go on one way.

Then you will need to seperate the two pieces that are "welded" together in this pic. I used a small pair of side cutters and pinched the pieces in two.



Next bend the top tab up and the bottom tab down. Then attach the diode just as shown is Jaak's pictures, with the silver line toward the bottom of the relay. and attach the wire on top and drill the hole just as Jaak has shown.

The wiring is super simple. The wire from the relay goes to either pin on the temp control. Attach it with one of the spade termanals provided in the kit.

The other pin on the temp control simply needs to be grounded. I grounded mine to the horn mounting nut(13mm)using the ring termanal provided in the kit. When finished it should look like this.

[95ttoplt1]

Next reinstall the front trim pieces




and enjoy the final product, all hidden, automatic, and adjustable.

[MagnumFreak]

great write up, moved into the knowledgebase.

[95ttoplt1]

Thanks, In the next couple of days I am going to make a dyno switch that will install in the same location.

It would just conect the two termanals on the Temp control when on, thus making the fans run. This would be used in a hood up condition on the dyno or between rounds at the track.

[1fastsedan]

I had the same idea, but haven't gotten around to installing it. I'm glad your works so well, now I'm definitely doing it. Thanks for the great write-up and all the pics.

[jay2puff]

great write-up thanks

[Rev.Hammer]

Very nice and neat! You did famously on this, Thank you!

[Cam]

Nice job!!. Beers and Cheers to you.

[nick_danger]

Awesome! Gee, an automatic fan mod... who-da thunk? Nice write up! BEANS!

[Hemi31]

While I agree with the idae I would use a sender that screws into the T-Stat housing or head.The Temp will be more accurate and you won't risk damaging the radiator with the probe.Just my opinion though.......great job!

[Big Boy]

Nice mod. And my mod list keeps growning.

[Token]

Did you solder in a 680ohm resistor between pin 85 & 86 on the Bosch relay? The factory relay has the resistor in place and without one you're likely to throw a code.

[95ttoplt1]

The relays I bought already have this resistor in place , I have driven around with these in and no codes



Hemi 31, I agree that you would get a more accurate engine temp, from my tests I don't think there would be any gain. My stat opens at about 179-181, reading this temp in the head wouldn't do any good IMO as the over temp(180+) coolant isn't in the radiator yet where the fans are. I have seen the probes in the fins like I have it on many cars before and never seen a problem. I agree with your concern though.

[Fast56k]

Might want to check the relay after some use. I bought an "auto" relay that seemed heavy enough from Radio Shack. I checked it after a day, and it had just started to cave in on one corner from the heat. The inside of that box and those relays get hot. I decided on the manual switch approach. Here is a picture of my switch placement in case someone is interested.

http://www.chargerforums.com/forums/...ad.php?t=24287

C.

Silver 06 SRT-8

[Jaak]

Good write up. Been talking about it for ages, glad to see someone actually did it!

Using the OEM sensor would be a good alternate as well, as a simple comparater circuit could be used, or even two, to select hi/low. But for most people this is the easiest way to do it. Just make sure you wire it to a hood switch that only grounds when the hood is closed.

Sure would suck to injure your local Chrysler Tech when he works on your car and the fans start up on their own.