Hmmm, seems like the system pressure may be borderline low. When things get hot, the refrigerant expands and the pressure increases to the point where the low pressure cut-out switch allows the system to run. Check or have the pressures checked.
Mystery 400E A/C Issue
1993 400E. A/C will not come on for maybe 30 to 45 minutes of driving and the engine and engine compartment gets really hot. Sometimes it comes on by itself and other times I have to restart the engine. When it does come on, it blows normal and the air is cold. Almost sounds like the heat is causing expansion of something until contact is made and it starts working again. When engine cools down, no a/c until things heat up again. I'm lost on this one. Maybe it's a wiring issue, but all mechanics want to do is to rebuild the HVAC system which is costly. Any thoughts would be helpful.
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On the receiver/dryer. There are two of them. One is a pressure switch that turns on the cooling fans when the refrigerant is compressed to "working" pressure. The other is a high-low pressure switch that keeps the A/C from working the if refrigerant system pressure is either too low or too high. They are different colors and I can't remember which is which.
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