I have a 2007.5 Dodge Ram 3500. My A/C is not blowing out cold air. I went to check the low side charge and noticed that my compressor was not running. I went inside the cab and turned on the defrost and still the compressor is not running. So, Ive concluded that either my coolant pressure is too low or I have a bad relay. Ive checked the fuses and they're good. My question here is how do I get the compressor to pull vacuum if it won't start due to low coolant pressure. I read about jumping my A/C switch to find that my truck doesn't have an A/C switch but it has a transducer instead. Any ideas? Any help would be greatly appreciated.

 

Need to check if there is any charge in the system. Set of R134 gauges would be helpful. Pulling the codes would be my first step. DTCs must be read with a scan tool once you pull code get back to us. I would guess the compressor clutch or system leak from compressor, evaporator or condenser. Check for any signs of refrigerant oil on ac hoses and condenser. Electronic Leak detector would be helpful, or add dye to system with a partial charge. UV light and glasses needed to check for signs of leakage.

 

I do have gauges but from what I understood in my reading is that the gauge cannot be considered accurate unless the compressor is running and pulling a vacuum on the system. Also, any ideas of where I might find my relay box. I looked in my fuse panel and there isn't a single relay inside, only fuses. I still need to check this relay and rule that out to be sure its not an electrical problem.

 

Most likely a bad clutch coil follow diagnostic to test coil. Paper clip can be used for back probe with a digital ohm meter. If you remove inner wheel well you can gain access to compressor without having to crawl under vehicle. I would also purchase a code reader to pull any codes that are stored.

 

No codes showing. Pulled the wheel well and tested the low pressure switch and confirmed that the plug to the A/C compressor itself has power. Is this the same plug as the "A/C clutch coil connector" or am I missing a plug? And thank you for the PDF it was extremely helpful.

 

compressor clutch connector, this is a 6.7 diesel but ac connector is in same location. If you have power and ground there, check resistance of clutch if not in spec replace compressor. I'm sure there is a code stored but code would be stored in the TIPM not in the PCM. Your code reader may not be able to pull that code.

 

The low pressure system switch is connected to the accumulator tank and is a two term push on switch. A paper clip bent to short the two terms together of the disconnected switch makes the AC clutch engage. Best let an expert play with this.