I have a 1999 Dodge Ram 1500 ST with a 5.2L engine. Recently, the radiator cracked, causing the truck to overheat. During this incident, the headlight and fog light wires, which had been rewired previously, melted and arced. I've since replaced these lights.

Currently, I have two main issues:

1. A/C Clutch: It’s not getting power. The relay gets power but doesn't engage. I've tested and swapped the relay with others, but it still doesn't work. When I send power directly to the A/C clutch wire, it turns on.
   
2. Overhead Dome: The unit that shows outside temperature, MPG, and DTE is not turning on at all.
   

All other parts of the truck, including the pressure switches, are getting power. I have checked the battery and alternator, and they are good. The radiator has been replaced and is working fine. I've tested the high and low-pressure switches and the HVAC control module, and they are all working. Additionally, I’ve checked the fuses and relays, and they are good.

I’m certain it’s an electrical issue but can’t pinpoint where the problem lies. Any help would be greatly appreciated.

 

Does the relay come on when ac is on? If so are you getting power past the relay?

 

On the 99, I think the relay is controlled by the PCM, PCM will only engage it if it sees voltage on the circuit for the pressure switches. Put gauges on it, see what your pressures are.

 

My 96 is controlled by the pcm. It takes the que from the hvac switch but will cut off the compressor under load. A few years ago for some reason it would not turn the relay on. I jumped it out so i could have ac. The next year it was working again. I believe the pressure switches are after the relay as a safety but they may have changed it.