LT1 dual fans manual switch

[Teds89IROC]

LT1 dual fans with the 3 relay system. They didn't come on with the computer when I first did the swap but they worked when i jumped the relay terminals. I figured I'd make a manual fan switch and be done. Following some threads I tried grounding out the green and blue wires on the C100 plug and and no dice. However when I put power to them the fans work. I was in a rush to drive the car so i setup a switch this way and the fans work and keep the car cool but I noticed when the car is running and I flip the switch it starts to get choppy, obviously not right. Key off I have constant power to the D and F fan relays. Blue and green wires are grounded. When I put the ignition on i still have the same constant power plus power to the white wires on the same relays. When I touch the grounded test light to the green and blue wires I get nothing. When I touch them with 12v the fans turn on. I also checked and the fan plugs are grounded.

I'm trying to figure this out and for the life of me cant. Any ideas??

[LTb1ow]

Whats it in?

[sweetbmxrider]

Are the fans wired into your stock wiring? I want to look at schematics to understand what you are saying.

[BonzoHansen]

this should be your setup, it is how GM wired the 4th gens with 3 relays. grounding the 335 and 473 circuits should trigger the relays. you said you had constant power, how about the switched power on the trigger side? what is your CTS reading? maybe its bad and the ecm is not flipping the fans on?




you know you really ought to fix the problem and not band-aid it with a manual switch. your car is too nice for that

[Teds89IROC]

I swapped in the rebuilt LT1 out of Bill's TA he sold to Alex. Added a CC306, LS1 lifters, roller rockers, hardened pushrods etc and a tune. factory aluminum heads for now till i can throw more cash at it. With the swap I used the LT1 harness, computer, and the underhood fuse box for ease. I stripped out and depinned the plugs/harness of all the uneccessary wires like emissions, ABS, etc and cross referenced to my bulkhead connector on the iroc firewall to use my factory guages.

Not sure what the CTS reading is, I know everything worked on the TA before my brother and I pulled the motor. CTS was my next thought last night. Like I said, its all basically setup plug and play from a 95 car. Not sure which is the trigger switch without looking at it.

[89 Trans Am WS6]

Ted is the diagram posted above what your working with? You mention a white wire but I dont see one in the diagram.. perhaps something got messed up when you repinned/stripped the harness?

it seems that your saying that you got power on the ign feed wire..but do you have power on the red fuse link wire? Thats the one that is actually powering the fans.

I really dont think CTS is your problem..since grounding that wire should really turn on the fans...

If your powering the dk blu and dk green wires and getting the fans to come on..something is not right. To me it seems like a ground is missing or a wire is crossed..looking at the diagram powering those wires should not turn on your fans..its not the right side of the relay to do that...unless your shooting power up say the blue wire..its going through the relays on the coil side and then grounding through the green wire..those activating the relays..again still not right..

Are you running AC still?

I would first check to make sure your setup matches the diagram. Double check that the nessecary pins are still in place.

Verify the ign on feed to the coil side of the relay gets power when you turn the key on. That would be D5 F5 & J5.

Also verify that you have constant power to the red wire.. D1 and F4. That should be from a fuse link under the hood and always hot.

Verify the cooling fan ground is good, and the ground J1 on relay 3.

Heres another diagram thats basically the same, but redrawn by mitchell. May be a bit easier to follow as its spaced out a bit more then the gm style ones.

Let me know how ya make out buddy.

Joe

EDIT: Are all 3 relays good? lol

[Teds89IROC]

Thanks for the reply Joe, I used a similar one and was surprised not to see any white wires either. But I did remove what looked like factory wire loom from the fan harness. The wires i depinned were all AC and emisisons related, i didnt touch anything else. But no, not running AC. And the relays were the first thing I checked lol I'll go through it again hopefully tonight and report back. I assume it's a bad or missing ground, something dumb off that fuse box.

[Teds89IROC]

Found the problem! I had constant power to D1 and F4 and proper grounds however ignition power wasn't being distributed to the fan fuse, so D5 J5 and F2 didn't have power. Looks like the brown wire had a few junctions and the other side was clipped. I soldered in a new wire and touching the blue and green wires with a ground trips the relay and fans go on. It was too late when I finished but tomorrow after work I'll let the car get hot and see if the fans come on via computer.

Thanks all!

[89 Trans Am WS6]

Very nice!

Im sure you'll be good, but if not now ya know that half of the ckt works properly and you rule that out of anything further.

[Teds89IROC]

Fans come on with the computer at about 160ish, went for a ride and it stays nice and cool

Next issue is I think IAC related, I'll make a new thread...