91 Z28, 350 tpi, auto

Having an issue with my fans not turning on at all, unless supplied directly with 12v. Basically, fans do not operate normally/automatically as they should. I picked up a new coolant temp switch today; haven't installed it yet, but thats what the diag pointed to. Whoever owned the car previously wired the dual fans together. Does anyone have a schematic for this mod? There is a few spliced wires at the relays, but I'm not quite sure how they should be for this. They operated fine for the past year and a half, so something had to go bad. Headed out now to replace CTS. Any other ideas?

 

Installed CTS, still no fans. Also, forgot to mention that it's spitting out code 15. Relays are hooked up the way they should be. Fans are still wired together. Everything checks out the way it should. Code 15 says to check connections to ECM (Haynes). Only thing I can think of is that maybe the ECM is starting to go? The car has been stalling/sputtering every now and then... Completely intermittent.

 

terminal "e" on the relays should have constant 12v, if not check the fusable links
terminal "d" should have 12v with the key on, if not check the fan fuse in the fuse panel
See this message for a diagram.

https://www.thirdgen.org/forums/tpi/...wire-help.html

 

First, thanks for the reply. Finally had a chance to do some troubleshooting today.

My problem seems to be the (250 BRN) wire going from pin 'D' on the fan relays going to the ignition. It does not lead to ground like it should and it only has 3.4 V with the ignition "On" instead of 12 V.

Still haven't checked it at the Bulkhead connector (G8)

Pin 'E' has proper ground and 12 V.

With pins 'A' & 'E' jumpered, fans turn on.

20 amp fuse under the dash is still good.

Side note: With my A/C on, the alternator does not charge the battery. Think this is related?

Hopefully it stops raining here tomorrow so I can mess with it some more.

Thanks again for the help!

 

Turns out Pin 'D' gets ground and 12V with the car running.

Replaced CTS: no change
Replaced Fan Switch on passenger cyl head: no change
Replaced ECU: no change

This car is really testing my patience!

I've traced wires, checked voltages, checked grounds and everything is checking out the way it should, but the problem still exists!

I'm at a loss...

 

well if you get tired of trying to fix the problem just toggle switch the ol bitch. probably not the best solution but it works for me.

 

Does the primary fan come on when you ground the aldl? It should to test the circuit.

 

"Does the primary fan come on when you ground the aldl? It should to test the circuit."


No, it does not.