yep another question about this issue. I recently bought a 1996 Grand Caravan with 3.8L that was in a minor front end collision. I replaced both condensers, radiator and hood. While trying to charge the A/C it was evident that the fans would not come on.

I used my Power Probe to check the relay plug --
Big gray wire +13.4V
Big green wire Ground (if you put 12V into this wire the fans will come on)
Little Black Ground

Little green/blue This is where it gets kinda odd -- it shows +12.7V and it should be a pulsed ground from the PCM

I have tried a couple of used relays from the pull a part

does this seem like a PCM issue? anyone have any experience with having a PCM "rebuilt" for $215

 

I should have included that the readings were taken with the engine running and the a/c button activated. I am not sure that the compressor clutch kicked on and I will check that this afternoon. After I replaced the condensers I pulled a vacuum and was able to get it to take two cans of freon before the pressures got too high and turned off the clutch. After setting a while the compressor would come on and run until the pressure got too high from no air movement and it would cool while driving. I will check the system pressures and make sure there is not a leak that has bled off the freon. My assumption is that the fans will not come on unless the compressor is running.

 

I have the same problem on my 98. The PCM control the fan speed and turns them on when the A/C is on. The only other thing to check before ordering a reman PCM is the sense circuit from the fan relay to the PCM connector: I think it's pin 2 on the fan relay connector and pin 73 on the PCM harness. The reading should be less than 5 ohms; if so, time to order a PCM; if not fix the circuit.

 

are the pins marked with numbers on the PCM?

 

Yes the PCM connectors have numbers on the connectors.

 

the PCM connector to plug measures 1.1 ohm of resistance -- rebuilt PCM time

 

I faked mine out by putting a relay across the fan controller contacts (3&4); use the AC coil voltage to energize the relay coil and ground the other side ( usually 85 or 86). Works great for the summer when the AC is on. It'll buy you some time to get a rebuilt PCM.