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High suction and Head pressures

mrpate on Sun July 01, 2012 3:58 PM User is offline

Year: 1967
Make: Chev
Model: corvette
Engine Size: 327
Refrigerant Type: R-12
Ambient Temp: 97
Pressure Low: 82
Pressure High: 345
Country of Origin: United States

I posted here about a month ago with a problem relating to low suction pressure and head pressure. It turned out that the new expansion valve I had installed was stuck in the closed position and I purchased a new expansion valve. After installing the new valve last week, I triple evacuated the system and did a final evacuation to 100 microns. Isolated the pump over night and the pressure did not rise above 220 microns. I believe this indicates that the system is leak free. I have installed a new compressor shaft seal, the new expansion valve, new condenser, had the filter dryer rebuilt and installed a new fan clutch and the GM seven blade fan.

Listed below is data that I took this morning in an effort to gather data to correct the problem.

Test 1 Conditions: Hot water valve disconnected and plugged. To eliminate the potential of the high head pressure being caused by a overcharge, last evening I bled off just enough gas to show bubbling in the sight glass. Blower fan on high and discharge temp of vent in cabin is 93 degrees. Ambient temperature is 90 degrees. Portable fan blowing on condenser.

Suction press Head Press Discharge Temp of vent
Time 1 minute into operation 64 22090 degrees
2 minutes 6226085
3 minutes 6128078
4 minutes 6330075
5 minutes 6530577
6 minutes 68 31580
7 minutes 6931582

At this point I beginning to think the new expansion valve is stuck open. I removed the J bulb thermal element and place in salt water ice bath that had a temp of 28 degrees.

I did not get but one minute into the test as the head pressure was 350 and rising. The suction pressure was 29 psig and I take this to be the pressure at which the POA is set.

Thinking perhaps that I may have freed up the expansion valve I decided to re-install the J bulb on the suction line. Blower fan still on high with the temperature of the discharge vent now at 97 degrees. Ambient temperature is now 95 degrees. Some bubbles in the sight glass. Portable fan still blowing on the condenser

suction press Head Press Discharge Temp of vent
1 minute into operation8531092
2 minutes8233089
3 minutes8134087
4 minutes8134087
5 minutes8234589

Suggestions Please? I do have on the shelf a older expansion valve that was functional but the bulb is the corkscrew style. It was functioning 3 years ago before I decided to rebuild the engine bay.


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