vjjack04

Guys I have this question on the LS1 tech Forum but they're not very good at answering like you fellas are. For those of you that have put a LS3 in your C2 with a GM performance ECM colon I'm trying to hook up the electric fans. I have a dewitts radiator with dual spall fans. 5 to 30 amp relays. I have the black wire grounded, I have two heavy-gauge yellow wires to 12 volt always hot. Then I have two smaller wires I think should be the ignition key. They are hooked to the blue wire from the ECM. Fans won't work had to LS running over 210 degrees and the fans won't work. If you've done this and you know something about it would appreciate any suggestions

Ken Sungela

Your description of your wiring setup is not clear, but doesn't sound correct.
I use a different brand ECM/harness, but it may be the same setup. The wires from your harness go to the ground side of your cooling fan relay. When the ecm calls for cooling, the blue wire gets grounded, then triggering the relay to send 12v to the fan.

The GM instructions say this (but not entirely clear IMO):
• A cooling fan is controlled by the ECM. Control is set to turn on a 12 V fan at 97 Deg C (207 Deg F) coolant temperature. The fan control wire is fused/relayed and must be connected directly to your fan.

This diagram may help if you also have vintage air.
https://www.vintageair.com/universit...rinary-switch/
The wire from our ECM/harness is the Optional Fan Temperature Switch in Engine (white wire) which is connected to Terminal 86 (ground side) of your cooling fan relay.

Take all this with a grain of salt as I don't know if you have the exact same setup. Fuse everything before turning on.
Hope this helps.

Robert61

Ken is correct. The positive wire to the fans are always hot. The ECM sends a ground signal to the relay which in turn grounds the fan. I also have mine set up where the ac pressure switch grounds the relay. Then on the front I have a manual fan.


On a side note how do you have the heater hoses routed?

vjjack04

I am using the new Earl's 90 degree swivel elbos. So i have all the heater hoses down low and actually going through the SRIII frame mount areas for the engine mounts...(If you look close it you may be able to see...I can take another picture later today)..So the hoses come out of the Vintage Air pass through area under the passenger fender, go along the back side of the passenger side inner fender well and then down under the motor mount area and into the 90 degree swivels. To use the swivels there are two sizes. (1) PART# SS988409ERL & (1) PART# SS988412ERL

vjjack04

Thanks Ken; I was trying to use voice to text and some of the wording got messed up in the original question...however, the info you provided, I believe, is what I needed. Thanks again.

Robert61

I'll make a suggestion tonite when I get home. It's too much for me to type on my ph.

Robert61

vjjack04

Ken,
Being as you we so good at explaining the above...I wonder if you have any advice for the situation I now have....I did hook up the blue wire as you mention...and then from the fans I have a "ignition keyed hot" hooked to orange wires on the fans...but what I have is when the car gets to the right temperature, the fans dont turn on until I turn the key off....then, the car doesnt turn off, the fans turn on and I get about 4-5 volts at the keyed circuit (which had 12+ volts before the fans turn on)...I wonder does my description make sense...? Is the solution to add a diode? I will be talking to a fellow who knows electrical stuff later in the week....but wonder what you, or anyone else who might have knowledge in this area thinks...?

j_66chevelle

I would try running the fans manual first before trying to get the computer figured out. If using the Spal relays and Dewitts dual fan setup (I have the same setup), the yellow wire is to the battery, red to the fans, orange is ignition, and gray is ground. Even if you ground the gray wire the fans will not come on unless you have 12 volts to the orange wire.
1. Ensure you have 12 volts to the yellow wire and the orange wire
2. Ground the gray wire, fans should come on
3. Next, place the orange wire back in the circuit, turn on the key, ground the gray wire, fans should come on.
4. Lastly, if the above works, the computer should provide a ground when a specific temperature is reached.

Hope that helps

Ken Sungela

As suggested above, test each part of your circuit for proper operation. You can draw a picture of your circuit and take a photo then post it. its difficult to understand how you have it wired. I'm a visual person, so a pic says a 1000 words to me.

Factoid

vjjack04

Thanks for the info above. I have it connected the way you describe. And i have tested in and the fans work when applying direct 12 v to the orange wire. What I have now is when the engine temp gets hot enough for the fan to come on, the fan doesnt come on, BUT if I then turn the car off, it keeps running, AND when the key is turned to the off position, that's when the fan comes on. So at that point the car is running, the fans are on, but I can even take the key out AND it still runs. Also at the bulk head where I have the orange wire connected, with the key off and only while the fan is running it reads about 4 and a half volts...I am going to try another ignition keyed wire when I get home today. I had someone tell me yesterday that I may need a diode....was wondering if anyone else needed or used a diode for this reason.

vjjack04

I am using the GM Performance LS3 (376/480) harness with their E67 ECM. It has a 58x crankshaft reluctor wheel.

Factoid

vjjack04

Ken,
i am set up like j 66Chevelle describes and have tested. The only thing I haven't tested is removing the triggered orange wire from where I have it on the bulk head (which is supposed to be a key ignition point for an electric fan according to American Autowire) and going directly to the battery. It seems that if I run a wire to hook it to the battery, and then run the car to get it to 207 degrees it should turn the fan on.

vjjack04

Factoid,
Thanks for that, that's why I am posting this, to get info on whether or not anyone has had to use a diode. So that's good to know (that its not needed). I will see if I can make a drawing with wire colors..(as I think it will be hard to get a good picture). Will have to do that later today when I get home.

Factoid

daz_au

I use the thick fan wire the GMPP harness provides (I think I remember its blue) and its connected directly to my SPAL fan. Since you have 2 fans I guess it requires a relay even though that output already uses a 30A relay and fuse within the controller. One thing I would note (as per the GMPP ECU instructions) is that the GM ECU doesn't switch the fan on until 207F, so maybe you are just not hot enough yet ? As others have suggested, you could just test the circuits separately, hook a bulb (or multimeter) to the ECU fan wire and a switch to your fan relays for manual operation. Run the engine up to 220, the ECU should light the bulb and you can hit the switch to start the fans and push the temp down until the bulb goes off. If those two things happen, then you should be able to trust the ECU and connect the fan output to the triggers for the Spal fan relays. I have to admit I spent some anxious moments watching the temp gauge the first time I let my GM ECU control the fans.

vjjack04

Thanks guys, I really appreciate all the solid responses...I am learning alot as I work through this conversion...This will be the only and last car I do this kind of thing to.

vjjack04

Here's how its wired now on my car....same colors as represented to the relays, battery (yellow), ignition (orange), and (red) to fans. So is it the fan ground that goes to the ECM or the grey wire?