1998 GMC Sierra

Air Conditioning problem
1998 GMC Sierra V8 Two Wheel Drive Automatic

I have been doing my own servicing of my air conditioning for several years. My system in my truck lost all refigerant in the system over the winter. When I initially started to check the system with my gauges the clutch would engage when the internal pressure would drop down and cut off when the pressure run up. This cycle would take place every 2-3 seconds and did this several times while the truck was running. Thinking the system was empty I purchased freon the next day but when I was ready to charge the system the clutch would not engage. Being as the compressor was already 5 years old I decided to replace the entire system. The new compressor still would not engage. With a vacuum already on for over an hour and oil and freon in the system I checked power to the high qnd low pressure switches and both were operation at the required voltage. Removing the signal wires fron the compressor I hooked up a live wire and ground from the battery and the cluth begin to operate correctly. I completed filling the system and have cold air again. Problem is it won't operate with the controls. I have checked the in cab fuses as well as the fuses under the hood along with the AC relay. All are good to go. I have power to the controls and the AC switch is energizing correctly. HELP!
March 22, 2009.

Do you have climate control or the manual system? If you jumper the clutch coil contacts in the ac relay socket does the compressor run? If no, do you have 12 volts at the socket? Witn the control calling for max cool do you have 12 volts accross the coil contacts in the relay socket? Please advise.

James W.
Mar 23, 2009.
It is a manual system.
And yes when I jumper the clutch coil socket the compessor runs and yes there is 12 volts at all contact points? Please advise.
Matt Myers

Mar 25, 2009.