Fans not working

[r00b]

A few days ago I put the A/C compressors belt back on and tested the car, turned the A/C to max. The fans kicked on with their usual lout sound, the next day I noticed my car was getting hotter than usual and that I couldn't hear the fans. Looking under the car the fans seemed to be spinning very slowly. I checked the fuses and fan relay and now my fans don't work at all, if the car is hot or the A/C is on.

Any Ideas on what could have failed?

[DeLorean03]

Go to the resources section --> All Wiring Diagrams. Look at the Cooling Fan Circuit.

Basically: 4 things or so that could have gone wrong: relay, fan fail device, otterstat, or your diode(s).

1. I would disconnect my otterstat, put the key in the position to prime the pump but not start the engine running, and jump the two wires (touch the ends of them) together. If that works and the fans come on, bad otterstat.

2. You could jump the two wires together as previously stated, and while they're jumped together, wiggle the fan relay and fail fail - something may have come loose.

3. If one of the diodes (symbol of triangle with line on the tip) went bad, that would cause a loss of current, which may explain why your fans are turning extremely slowly. I could be totally wrong there, and I've almost never ever heard of the diodes failing. Dave (BitSync) could chime in far more accurately on that one and how to test if the diode(s) have gone bad I'm sure.

4. Possible that your circuit breaker is acting up too. I don't know if you could swap out one of the other circuit breakers in the car or not to test. I'd personally just get a spare and swap it out before tearing apart any other circuits in the car.

[Bitsyncmaster]

Go to the resources section --> All Wiring Diagrams. Look at the Cooling Fan Circuit.

Basically: 4 things or so that could have gone wrong: relay, fan fail device, otterstat, or your diode(s).

1. I would disconnect my otterstat, put the key in the position to prime the pump but not start the engine running, and jump the two wires (touch the ends of them) together. If that works and the fans come on, bad otterstat.

2. You could jump the two wires together as previously stated, and while they're jumped together, wiggle the fan relay and fail fail - something may have come loose.

3. If one of the diodes (symbol of triangle with line on the tip) went bad, that would cause a loss of current, which may explain why your fans are turning extremely slowly. I could be totally wrong there, and I've almost never ever heard of the diodes failing. Dave (BitSync) could chime in far more accurately on that one and how to test if the diode(s) have gone bad I'm sure.

4. Possible that your circuit breaker is acting up too. I don't know if you could swap out one of the other circuit breakers in the car or not to test. I'd personally just get a spare and swap it out before tearing apart any other circuits in the car.

Good writeup.

Most common is the fan fail jumpers get worked loose. I have see intermittent connections at the diodes but that usually results in only the AC not turning them on. Another common fault is a pin gets pushed out of the relay sockets.

Lastly this rare fault I just had on my car was a bad ground wire on the fan relay socket. The grounds for the relays are a daisy chain from the far right relay to the next, and so on. So the fan relay and fan fail are the last sockets in that chain. So intermittent crimps are possible and are the hardest things to find. I found my with an ohm meter by accident since my solid state relays worked fine with that bad ground.

Edit:
On second thought. Maybe these bad crimps are not as rare as I thought. I found another one in my bulkhead connector a few years back. That was in the starter (bypass circuit). I could not inspect that crimp since it was on the socket side (inside the pontoon).

[David T]

Very common for the circuit breakers to fail. Get the "Relay Upgrade Kit" if it has not already been installed. Included are uprated circuit breakers for the cooling fans and the heater fan. Also inspect whatever you have for installed for the Fan fail Relay. If you still have the blue relay then it has failed.
David Teitelbaum