2004 WJ with 4.0, my fan don't work. I have replaced the fan, PDC relays and the coolant temp sensor. There is no secondary relay to be found and I was wondering if the high low pressure AC switch could be the problem? But if its bad wouldn't my AC be non functional?

 

Have you hot-wired the fan to see if it runs?

 

Roger that its a brand new fan.

 

Okay, the double fan relay system is beyond my experience, but I believe they get their triggers from the PCM reading the temp sensor. One's for high and the other for low. That was supposed to eliminate the problem of the pulse-activated one on the earlier models from getting hot and failing. When the relay on mine died, I just wired a relay and switch to the fan so it would run anytime the ignition was on until I could get a relay to replace it. I left that circuit installed after I replaced the relay so if the new one failed, I wouldn't be left stranded on the road.

 

so you replaced the relay under the passenger headlight?

 

Yes, but it was a couple of days later when I had the time. It was cold, rainy, and I was working in my driveway. His system is different.