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High pressure on low side

rschmitt2 on Sun August 24, 2008 4:32 PM User is offline

Year: 1992
Make: Plymouth
Model: Colt Vista
Engine Size: 1.8
Refrigerant Type: R134
Ambient Temp: 89
Pressure Low: 100
Pressure High: 170
Country of Origin: United States

The AC is a 134a retrofit. It works well with cold output air. However, when it has been running a while and you stop the car to go in a store, when you come out and switch the AC on again, the compressor won't come on. You have to wait many hours (sometimes overnight) before it will work again. While in this condition, I hooked up the hoses and get 100 on the low side, 170 on the high, with 89 degree ambient temp. If I bypass the high pressure cutoff switch, I get cold air, but the low side pressure stays at 100. Any ideas?

mk378 on Mon August 25, 2008 9:59 AM User is offline

You cannot get any cooling while the low side is really 100. Measure pressures with the valve wheels on the manifold closed. Also be sure the couplers are properly coupling to the car.

Sounds like a bad switch, or it could be the clutch gap. Working when it is cool under the hood but then not engaging after the clutch coil heats up is classic clutch gap.

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