I have a 1987 volvo 240 wagon that I converted to R134-A about 3 months ago. I bought a kit that had the compressor, dryer, expansion valve (not an expansion tube), and oil included. I flushed the old hoses and put the system under vacuum for 45 minutes before adding approximately 3 12oz cans of R-134A. After the retrofit the cooling was not great but it would consistently cool the car to a comfortable temp as long as you were not sitting still in traffic.
In the last week or so I noticed that the car would cool well when first started, but would start to get warm after driving for 10-15 minutes when it was hot outside (on days when it is below 80F outside I had no issues).
I thought it might have a slow leak so I added 1 can of R134 (did not help) and then 2 additional cans with no improvement. I thought it might have a large leak so one of the cans had UV dye and I checked for leaks and found none. I noticed that when it is not cooling there is ice on the large tube that leaves the expansion valve into the evap coil. Also when it is not cooling the compressor runs constantly and does not cycle on and off regardless of the position of the cooling dial selector in the car (my car has the red and blue dial to engage the compressor), unless I turn the dial all the way off. I checked pressures and found that the suction side reads 0 psi and the discharge side read 175-200psi (after driving the car on hot day and noticing no cooling). If I let the car sit for a few hours and check it I get 25 psi on the discharge side and good cold air for 10-15 minutes, then discharge goes to 0 psi again and cooling stops. The sight glass does not show any bubbles.
I was wondering if it could have something to do with improper insulation around the expansion valve area. The old valve I took off had black putty type insulation around some of the copper lines that came off the valve but none around the valve it’s self. I tried to put it back like I found it but I lost some of the putty and it is not insulated as well as it was. Also, could water in the system cause these symptoms? We ran a vacuum pump but I am not sure if the pump we used was working properly. Could I have over filled the system with R134, and would that cause these symptoms? I have read that some people put electric pusher fans on the condenser coils to reject more heat – would that help this? Any ideas on what to do to fix this would be greatly appreciated.