Heater motor quits working after 45 min or so you can leave the fan switch on and 20 or so min later it will just starts working again seems like either blower motor is getting hot and shutting down and after it cools it comes back on or relay but I dont think this truck has a physical relay
Nope. The laws of physics have been rewritten and switches and relays no longer work because they were too reliable. There is a power control unit in the dash. It's a computer module that pulses the fan motor with a varying "duty cycle" to vary fan speed. Duty cycle means the percentage of time the motor is turned on compared to off. That was done in response to people not being happy with just four fan speeds. The computer can vary the speed from off to full speed and anywhere in between. This is critically important, and this type of insane reasoning is why I refuse to give up my '88 Grand Caravan and buy something newer.
As with any computer module, they have a high failure rate. Heat is also the deadly enemy of anything electronic, so you know it's going to have problems. That module sits near the bottom center of the dash. Check for loose plug connections, but suspect the problem is inside the module.
January, 4, 2012 AT 4:24 PM
Thank you I figured it was something along those lines but wasnt sure where to look. I had a problem about 4 months ago the computer board that is part of the fuse consolidation it shorted out on the wiper side and caught fire melted everything in that panel never blew that first fuse and didnt even discolor any wires or plugs that go in to it 450.00 put new one in every thing worked no lights on dash more luck than since thats when I found out no more relays but thanks again for the knowledge!
January, 4, 2012 AT 11:46 PM
Very happy to read it's fixed. I helped a friend rebuild a smashed '07 Dodge dually diesel last year and the integrated power module cost him $800.00. Only the backup lights, motorized pedals, and 4wd lights didn't work. I easily bypassed the lights and pedal problem by wiring in simple, reliable, inexpensive relays, but he had to spend the money to get the 4wd lights working so it would pass the state inspection. Thank you, you insane engineers. It's no wonder there are so many people who don't want to own new cars.