memoniz

I have a '96 F150, reg. cab, 300, auto. I recently replaced my a/c compressor and had it charged. I try not to use it that much but it's that time of year. When I turn on my a/c it runs fine for a while. But the longer it runs, my amp gauge starts jumping around and the battery light comes on and off. Also my temp. gauge goes up. When I shut the a/c off, everything goes back to normal. Turn it back on and it does it again after a short time. Then sometimes it doesn't happen at all. I'm pretty sure the temp goes up because the engine seems hotter. Also the a/c comes on when I set it to window defrost. Is that normal? The gauges don't move in that position. Alternator has been replaced recently too. Any help would be appreciated.

Bennyv83

When the compressor was changed, they might have removed or not changed the diode that is in series with the compressor wiring.
It prevents back-EMF generated by the compressor from screwing with the charging system.
Yes it's normal the AC runs in defrost, it dries the air before it comes out the vents, drying your windshield.

memoniz

Thanks for the information. I replaced it myself and didn't change any diode. I'll look into that. Thank you.