So I have come here hoping to get help with this problem. I have an 02 Ram 1500 SLT with a 5.9l and I cannot get the condensor fan to kick on. New fan, new compressor, good charge. No power at fan but fan works. All the fuses are good as well as the relays. CEL is on with P1491 code. Clutch will continue to cycle and not blow cold air. Have replaced the entire fuse panel and no luck. I am at a loss.

 

I believe it's whining about the control circuit for the fan relay.

 

What controls the relay?

 

Quite likely the pcm, or TIPM..... Got wiring diagrams? The relay is likely powered from the ignition switch, and grounded by the tipm, or pcm, when engine temp gets to some certain point, or, a/c is requested. This is where a service manual comes in REAL handy....... (and the electrical engineering degree......) Neither of which, do I have.

 

That is what my conclusion has been as well. That is the only thing I haven't replaced and cannot really troubleshoot through. I reset the CEL and it comes back on as soon as I kick the A/C on and the compressor keeps kicking on. Have you heard of anyone flashing it and being able to fix this problem? Know where to get a new one?

 

Seems more like a physical problem, rather than programming. I would suspect a bad connection, or broken wire, in the control circuit.

Ok, looks like the control circuit is powered via fuse 39 in the TIPM, control circuit ground is indeed controlled by the pcm, Dark Blue/Yellow trace wire to connector 2 pin 17 at the PCM.

Check the fuse first, if that's good, see if you are getting power on that wire at the PCM, engine running. A/C doesn't necessarily have to be on.

 

Stupid question. How do you tell if those fuses are bad or how do you test them? They are the clear top fuses. I figured you should be able to tell just by looking at them. I have a relay tester so I can test the relays. I will have to move the fuse panel so I can get to all the wiring. I will do this tomorrow and get back to you. I haven't had my A/C all summer and have never been this defeated by a vehicle.

 

Fuses are cheap enough, just replace it. According to theory, you can pull it out, and look at it to see if it's blown, but, I've had fuses that *looked* perfect, but, were still blown......

 

Ok. So fuse 39 is a spare. Relay 70 is the A/C condensor fan relay. Fuse 12 is the A/C condensor fan fuse. That is by the lid. No blown fuses or bad relays. No power at relay.

 

So...in my haste to fix my truck I put the wrong fuse panel on there. Things weren't lining up while troubleshooting it. Had my friend come over to start chasing wires and we both scratched our heads when trying to chase the power through the circuit. Realizing the fuse box was out of the correct year truck, not the correct model or engine. Went to the junkyard and lucked out and got the right one with the correct lid. Put it in and miraculously it worked. Large oversight on my behalf, lesson learned. Thanks for the insight.