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If the compressor kicks on, it's usually the orifice / valve that is the issue. Sometimes the Dryer clogs, or orifice , usually from rust or dirt in the system.
When the compressor kicks on the idle should drop, as it adds a load to the motor. Most idle stop solenoids do not have the power to push the throttle up, but can maintain the higher idle.
Update: I installed the missing thermal fuse and bought a set of gauges that have the right connector that will depress the shrader valve. The loaners from Autozone don't work with R12 valves. I watched a couple videos on using the gauge manifold and filled the system with R12. It took about 2 1/2 lbs. Now blowing out of vents at about 48 degrees. Thats good enough for me. Thanks for all the help and guidance. Lets see how long it keeps working. I still have a dozen 1 lb cans od R12 on hand.