My cooling fan isn't coming on and I bought a new control module and still not coming on.

I did some diagnostics and it seems to be getting power into the control module from the red small wire, and one of the large wires (forget which one). Continuity is fine on the grounds.

The one that has me stumped in the gray small wire. The voltage varies from between 1.5volts and almost 4 volts.

I believe that is the wire that comes from the pcm. . What should the value be?

Fan never comes on even when turning air con on.

Any assistance is appreciated.

 

Have you checked the 50 amp fuse in the black box next to
the Battery?

 

If he has power on the heavy read lead, that fuse is OK.

 

That lead comes from the ECU/PCM. It is a bidirectional data bus that the FCM and ECU use to communicate. Measuring it's voltage tells you (almost) nothing. You must look at the width of the pulses coming from the ECU to know what the ECU is telling the FCM.

OR, you can do this. Start engine when COLD. Fan should not run. Turn on A/C. Fan should run at low speed.
Now, CUT the gray wire, the fan should take about 30 seconds to warp up to very high speed (this is emergency mode, the FCM knows it is not talking to the ECU so it is trying to protect the engine). What also happens, is the ECU knows it is not hearing from the FCM so it lights the little "radiator" or "coolant" light on the left end of the instrument panel.

Now, that this information and continue your diagnostics.

One more thing, there is a SMALL wire (red/gray I think) that is 12 volt switched directly from the ignition switch - does it have power on it when the key is on?

I do have a criticism for you: Troubleshooting the electronics of the car without using the service manual is, generally, a waste of time. We can help you a lot, but even after reading my text, the manual will help you a lot with wire colors, connector pinouts and theory of operation (tho I admit the service manual was written very light on theory as they assume the average "mechanic" cant understand electronic theory anyway).

 

If the fan refuses to run and the coolant light never comes on, I'd read that as either a bad ECU (never happens) or a bad FCM that lies to the ECU and tells it all is OK, but it's an FCM that is not actually operating the fan. I've seen ONE FCM do exaclty that, but most of the time, the coolant light comes on as the ECU knows the FCM is not really working.

Also, keep in mind that light is a light bulb, if it is burned out you have no way of knowing. Also, the cooling system is not part of the emissions, so no "Check Engine" or diagnostic code will be generated.

 

Doesn’t the coolant light test when the key is first turned to on and the dash lights up?

 

Appreciate that info. More info I’ll keep with my Fan documentation notes