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The $40, Temp-Sensing Fan Mod

56K views 85 replies 24 participants last post by  GoldNnasty 
#1 ·
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.

 
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#64 ·
I'm postin best wishes to Bob in the other thread, ya'll got me dizzy following these two. The other being jaak's mystery wire post.. lol

Jaak do we have a source for the stock relays that you are modifying?. You must at the rate you are using them up. I wanted to leave my orig in tack and grab a few to experiment with like yourself.
Was thinking if we could find a good price on a lot of say 20? I might setup and do the mod and let the guys have emm for whatever the cost is. Just a thought.

BillyD.. :thumbs_u:
 
#68 ·
More about my fan shroud today, I got the chance to look at another Magnum RT - namely the radiator and the shroud. This car also had room to plug in the temp. probe, my RT does not! Oh well, I will find a spot to plug that sucker in. I guess there is some play or room, to mount the shroud one way or another - some extra clearance.

Cooler weather is here in Florida now, so no big rush to get the fan mod working.

Bob
 
#70 ·
Finally found a spot to insert the temperature probe in the radiator, spotted it while doing the Blink-Blink mod. Hope to finish up the fan mod install today, my relay is all set to go and I tested it this morning, turns both fans on when I ground the wire.

So cool!

Bob A.
 
#71 ·
This is a Great Mod! :friday:

I have a question:
Does the coil of the aftermarket relay need a resistor in parallel to keep from throwing a CEL? (if you use the original relay it has the resistor)

I have been reading waaaaay too much lately, and it appears that the factory manual shows a resistor???

Thimpkin waaaay tooooo much:mrgreen:

:popcorn:
 
#72 ·
This is a Great Mod! :friday:

I have a question:
Does the coil of the aftermarket relay need a resistor in parallel to keep from throwing a CEL? (if you use the original relay it has the resistor)

I have been reading waaaaay too much lately, and it appears that the factory manual shows a resistor???

Thimpkin waaaay tooooo much:mrgreen:

:popcorn:
You don't need the resistor if you use the Bosch part number listed above. It has the resistor built in and is working fine in my car.
 
#74 ·
Okay guys and gals, I am done!!!!!!!!!!!!!!!!!

Just finished up my fan mod right now and it works great!

Fans kick on when the engine temp gets to 180-182 degrees, cools the engine down to 179 real quick..............then shuts the fans off.

Took a picture of my install will try to post it here, may have to shrink it down. I mounted my temp controller a little different from Troy's, I mounted it in the engine compartment (out of the rain) on the fenderwell, near the fuse box. There is a metal tab there, not being used by anything. I also ran the ground wire to my mount bracket for the fan controller, short wires and easy to get to. I still want to install a inline fuse somewhere in the groind circuit - just for safety sake. Can just pull the fuse if I ever have to take the car in for service, so the mechanic does not get hurt by the fan.

Thanks again Troy for all your help!

Bob A.
 
#77 · (Edited)
ok, i just did the mod.

if you want, you can go back and add this to the first post.

the napa part number for the relay i gave is a CHINESE copy of the bosch. it is the hardest of the three to modify, imo.

i chose to use a preset 180 t-stat, and for my fan control i bought a Hayden fan t-stat part #3652 at pepboys, another part number that auto zone uses is 226206. this probe is self contained with the switch and is real easy to install.

this is a small probe that is preset at the factory to come on at 185, cut off at 170. its <$25 and the best part? it comes with a relay with the resistor installed. i opened it up and it is pretty nice. i modded the factory one and kept the other one as a spare for service calls. so the napa 191 ran 6 dollars. so i got the mod down to 31! no additional parts needed!

you dont need the harness in the picture...
 
#79 ·
Sorry for the delay on the alternate way of modding the stock relays, I've been kinda busy!

I have taken some pics and need to finish up tonight.

If the Bosch relays are easier, I say buy them and do the mod!
 
#80 ·
Has anyone from Central Texas done this mod? Specifically from Austin / Killeen area? I know it may look easy, but when it comes to electrical, it scares the sh!t out of me. I can't solder for crap. I may even consider Houston / Dallas in the mix. I have family I can visit (as an excuse to travle specifically for the mod)...shhh, don't let the wifey know, She doesn't understand the obsession!!! :) Any takers that wouldn't mind walking me through this in person?

Oh, not to take away from the post / instructions, but like I said electical and I don't get along. My luck is I would turn a vehicle that I paid 36K for, and that's only KBB'ing around 12K into scrap metal prices!!
 
#83 ·
interesting, but would like to have the photo's back.
 
#85 ·
My mod came out looking like a baby kitten.

Is there any way to do some screenshots of older posts to preserve the images. What happens to them? When they leave the forum do they get deleted?
 
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