My a/c system is all new less the evaporator. It is fully charged and converted to R134. When I press max the compressor turns on and the cooling starts. It cycles on and off but the vent temp only reaches 48 degrees F. When I bypass the cycling switch and the compressor runs continuously I get 35 degrees F at the vent. Is this the ATC preventing me from freezing in the car, or is the cycling switch/temp probe in the capillary tube ( is there a special grease that goes in there that would slow down the reaction to cold ? ) sensing cold too quick and shutting off the compressor ?
A/C cooling question 1988 5th ave
- Thread starter Master M
- Start date
Aspen500
Well-Known Member
One thing that comes to mind is the amount of R134a that was put in. It should be about 80% of the R12 capacity. If it's 32 oz R12 you only need 26 oz R134a (for example). If there's too much refrigerant the high pressure cutoff will shut the compressor off, just like when the pressure goes too low. When converted, the low pressure cycling switch needs to be replaced by a low/high pres cycling switch. Screws in the same place and uses the same wire/connector. The system will shut the compressor off to prevent the evaporator from freezing up and blocking air flow. It doesn't freeze internally but condensation will freeze on the tubes and fins and then the air gets warm until the ice melts off.
The sensing probe and capillary tube on the expansion valve, if faulty, can cause the valve to open more than it should and with a bigger orifice, the refrigerant won't be as cold.
Not super familiar with the '80's ATC systems but those are a couple things to check anyways.
The sensing probe and capillary tube on the expansion valve, if faulty, can cause the valve to open more than it should and with a bigger orifice, the refrigerant won't be as cold.
Not super familiar with the '80's ATC systems but those are a couple things to check anyways.
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The system calls for 42 ounces of R12. The AC had a leak at a fitting and the air was not cool at the vents. I added 2- 12 oz. cans of R134 and the high and low pressure on the gauges were 35 psi low side, and 140 psi high side.
