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Discussion Starter · #1 ·
I'm doing the 86/87 ECM swap this weekend on my Hot Air T. I have electric fans already installed but my old aftermarket fan controller doesn't seem to be working. A friend is telling me to just by another aftermarket job. I figured while I'm doing the swap I might as well use the ECM with what ever wires and relay I get out of the donor car for the fans. With that the fans will turn on with whatever temp the PROM tells it to correct? Does anyone know what temp the Thrasher chip is set for? And does anyone have any better ideas for fan setup? Thanks all.
 

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I'll be doing the same thing in the near future. Thinking I'd make it plug and play I went ahead and bought one of caspers fan relay wiring harnesses. It does hook up to factory wires (no drilling holes in firewall), but is only a single speed, and has a generic connector on the fan end.

My understanding is you hook it up to the low speed (high only used when AC on). With my cooling system upgrades I don't expect needing high. If so guess I'll just have to tag a relay on the AC hot wire.
 

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Discussion Starter · #4 ·
Steve, sounds like I should take warning from the fact that you have felt the need to create a fan troubleshooting page and do an aftermarket wiring relay instead. Looking at the diagram the stock ECM controlled system seems alot more involved than a simple dual fan controller like the broken one I have now. I simply want a single speed fan system that comes on at around 170 degrees. I also should mention that I have a V8 3 core radiator. I'm open to hear opinions on whether to wire it up stock or do another aftermarket deal. Let me know what you think fellas. Thanks
 

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No, the fan circuits are very simple but many are not used to trouble shooting anything electrical so I have started a simple trougbleshooting guide...I included the diagram for those that are used to using a meter but simply need access to the diagram.

If you ignore the delay circuit which is not needed anyway....there are two relays that control high and low speeds...if you have two fans, you can hook one to a relay for low speed and the other fan to the another relay for high speed.

In essence, all you have to do is run a wire from the battery thru a fusible link for safety to the relay power side, and come out the other side to a fan. From the relay trigger side go to a fused source of power that is hot when the key is on, and on the other side of the trigger part of the relay, go to the appropriate connector on the ecm....that will make your fan turn on when the temp is reached that is programmed into the chip.

For the other fan, instead of going to the ecm, buy a fan switch sensor form Jegs, or whomever, and install it where it is in the water stream....the other connections are the same...



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Discussion Starter · #6 ·
Okay that sounds good. Only question I'm left with is on the relay which side is the trigger and which is the power. I assume I could determine this when taking them out of a car but I thought I'd ask to be sure. Thanks abunch.
 

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If you are using an aftermarket relay it will come with a wiring diagram for the prongs on the relay. Normally, trigger circuit will go to prong 86 (this is the wire from the fused key on source). The ground side of this is prong 85 which goes to the ecm or to a thermal switch that goes into the water jacket.

The power from the battery (use a 10 gauge, or larger, wire) goes to prong 30. There should be a fusible link, or maybe, a slow-blow fuse in this wire. Prong 87 goes to the plus side of the fan.


Now, if you are looking at a factory relay/harness, the heavy red wire is on prong 30.

The brown wire is the trigger feed from the fuse block, the green (or the green/yellow) wire is the ground side prong 85 which goes to the ecm (green wire) or the fan coolant temp switch (green/yellow).

the last wire is either black/pink or black/red and comes off prong 87 going to the fan plus side.



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I'm in the "Learning from my mistakes" stage. I will be running a F-body aluminum 1 5/8" core, 20 fpi count rad with one of ramchargers dual fan setups on a hotair. I can't forsee a cooling problem.

Do U think I'm wrong?

Thankyou, Kevin
 

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Discussion Starter · #9 · (Edited)
Finally getting around to doing this since spring has sprung. Steve you said for the other relay to wire it to a fan switch sensor like this I assume
http://store.summitracing.com/partdetail.asp?part=PRM-19003&view=257#largerimage
The system I have in their currently that isn't working is an adjustable fan controler that has a dial to adjust the temperature the fans will turn on. Seen here
http://store.summitracing.com/partdetail.asp?part=DER-16759&view=257#largerimage
I don't think I can use the sensor that fits in the water jacket for this system can I? It would be easy to just wire the existing sensor to the relay I cliped from the yard. LMK if this will work.
 

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Unless I am confused....which is pretty often...why not use the GN coolant temperature switch that goes into the top of the intake on the drivers side of the throttlebody?:)
 

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Discussion Starter · #11 ·
I'm a hot air so are you speaking of the sensor in the front of the manifold located on the side of the water inlet. Seen here

Actually which one is it the one on the left or the right? Thanks.
 

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No...I was thinking you were swapping engines and not ecms only.

I don't know if the hot air cars had a coolant temp switch....they would not if they did not have electric fans...but...some hot air guy could add to this...

You can use an aftermarket switch as well as the 86/87 gm part...just need a coolant passage to screw it into.
 

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Discussion Starter · #13 ·
THanks Steve, I believe the temp sensor on the hot airs is actually right in front of the manifold and below the water neck. It would only serve the warning light I should think. I maybe able to plug into that or swap it with an 86/87 sensor and go from there. Can anyone verify this?
 

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the ic cars had three sensors...

the two by the neck fed the ecm temperature from one, and the idiot light on the other. Then there was a third one on top of the manifold on the drivers side front that was a switching sensor that turned on the high speed fan.

:)
 

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I'm helping my neighbor convert his F150 from a mechanical fan to an electric and I found this on a Jeep enthusiast's webpage:

Imperial electric fan adjustable thermostat #226203
(Advance Auto - about $19.00 ). If it's still available, it looks like a simple deal. Has a sensor bulb that mounts to the radiator fins.

Here's some pics of it:



 

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Discussion Starter · #16 ·
Yeah looks simple enough and cheap. Supposedly they have it in stock. That would then do away with the relay business and I would just wire my fans directly to it. I'm I right in this understanding? Thanks
 

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Discussion Starter · #18 ·
Okay so it just provides the signal to the relay. I pulled some relays out of the yard to use. Will they work. There must be a difference between the high and low speed relays. Should I buy the specific high and low 86/87 relays to use?
 

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You guys really like band-aids...:)

The relays are the same...probably should be at least 30 amp rated. Otherwise, a relay is just a heavy current switch.
 

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Discussion Starter · #20 ·
Bandaids? So what makes the high speed vs low speed?
 
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