Just recently charged system to correct pressure to a 1999 Dodge Ram truck V8. The only way I can get my compressor to come on is to jump it straight from the battery. I have power on my low pressure and high pressure switches. I have power going from my fuse to my a/c relay but have no power coming out. The four wires in this relay are 1) the hot from the fuse 2) the wire coming from the compressor 3) a wire going to my dash somewhere 4) the other is going to the power train control module. I tested all these wires and the power train control module wire serves as a ground with my test light. With all this information, my question is... in my a/c relay the hot wire from the fuse jumped with my compressor wire brings my compressor on - something in the systems has to automatically make this happen. Obviously the wire coming from the power train control module and/or the wire coming fromt he dash but how does this work? Can somebody tell me? Is there something else I can troubleshoot? If you could email me directly that would be a great help to me as this is my first time on this website and I am not sure I could find your answers. Please email me at chevy4ted@earthlink.net Thank you. :banghead: