Engine Size: 250
Refrigerant Type: R-12
Ambient Temp: 80
Pressure Low: 70
Pressure High: 100
Country of Origin: United States
I once again need your help. I last posted on August 14, 2014 under the thread R12 Oil. I had recounted how I removed the a/c components from my 1978 Ford Granada and installed them into my 1979 Ford Granada. I performed a vacuum test once a week for four weeks. The test was for six hours and I never saw the gauge needle drop. I was pretty confident that there was no leak so I tried to charge in a 12 oz can of R12. The system wouldn't suck in the refrigerant so I swapped out the expansion valve and stv assembly. I ultimately charged in four 12 oz cans of R12 refrigerant and the a/c cooled to 35 degrees.
For the past year I have enjoyed driving in relative comfort, due in part to the air conditioner. In the last few weeks I noticed that the cooling was between 40 and 48 degrees. I suspected that I once again had a leak and last week I only got 48 degrees but the air was still cold.
Yesterday the a/c failed completely with no cooling. I got out the vacuum pump and gauges to check for a leak but first pushed in the schrader valve. I was surprised when a blast of cold refrigerant shot out. The ambient temperature was 80 degrees when I connected the gauges. The low side showed 80 psi and the high side showed 80 psi. I started the engine and the low side dropped to 70 psi and the high side increased to 100 psi. The stv was completely covered in frost but the expansion valve was dry as a bone.
Any input would be greatly appreciated.
Assuming you're measuring the low side before the STV, it is likely that the STV is stuck in the nearly closed position, causing an almost total restriction of the flow. You probably still have a full charge of refrigerant.
Thanks again mk378,
I might be able to buy another stv on Ebay. I've seen them offered for sale. Is there any chance the expansion valve is the culprit?
Thank you Dougflas. In an attempt to test the expansion valve, I can heat the sensing bulb with a heat gun and cool it with a can of freeze spray. I will connect the gauge set to the low side and high side. Last week with the compressor engaged I saw 70 psi on the low side and 100 psi on the high side. Should the low side pressure change as I heat and cool the sensing bulb?
Also, I saw the exact suction throttle valve I need on Ebay. The seller wants $95 for it. The expansion valve is no longer available so I'm out of luck if the expansion valve in the car is bad. I have to pay another $35 or so to have the refrigerant recovered and $60 for three 12 oz cans of R12. So, to work on my a/c again will cost approximately $200.
I drive this car only once a week - I have to move it for street cleaning - and now it looks like I'll just leave it in the garage during hot days.
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