So, you fellows are awfully smart and I want to run this one past you, it’s got me befuddled.
I’ve been trying to diagnose Mary’s Ford Ranger which has some A/C issues. She thought the A/C didn’t work at all, and drove 6 hours in the heat without it… It actually does work, but only after running the engine for approximately 20 minutes. It can be running at idle, or on the highway, the timing is the same. Usually it comes on for a bit, then stops, then comes back on to stay. Once running it works great until you shut the engine off again for a long time. Brief stops it will still take a minute but comes back much faster. This makes me think the problem is somehow temperature related.
I’ve checked the refrigerant pressure, it is within the “good” zone while the compressor is running. Also when it does come on, it feels good and frosty. Could low refrigerant cause this somehow? The compressor does not even kick on for 20 minutes, which is the strangest part of all this.
If it’s freezing up, wouldn’t it cool first and then stop? It seems to work indefinitely once it starts.
If it’s airflow related, it would not come on parked at idle, which it does (eventually).
If the compressor was overheating, it would work at idle but not while driving. So it’s not that either.
For what it’s worth, the blower resistor is also bad, only the high setting works. I believe that is unrelated, and all my testing has been done using the high setting.