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Too hot for the AC

I have a '97 Mazda 626 with factory air. Most of the time, the AC works and works well, especially when it is cool outside. However, if it is a very warm day (90+) and I park the car in the hot sun, the AC does not work when I start the car. The green “AC On” light indicates it is on but the AC clutch does not engage. If I park the car in the shade and leave the windows open so that the interior of the car does not heat up, the AC will always work (provided I turn it on) not matter what the temperatures is outside. When the AC does work, it will work even when I drive the car in the hot sun and in high temperatures and it will continue to work as long as I run the car with the AC clutch cycling as needed to maintain temperature. The AC will always work in the morning after the car has sat out all night in the cooler air.

It appears there is a switch or relay that does not work when the car’s interior becomes very hot. Do you know which electrical component might be the culprit and where it is located for me to replace it?

The only switch I can think of off hand is the refrigerant pressure switch. Not sure how its causing the problem but I can’t think of anything else.