Appreciate your help with this air conditioner issue.
• Have an ’94 S550 Coupe with 420K miles. Replaced compressor and expansion valve about 150K miles ago. Worked well until a month ago. Found dye on the bottom of hose from the compressor. No rear air conditioner unit.
• Replaced a leaking hose from the air conditioning compressor. Changed dryer. Pulled vacuum, inserted a few oz. of PAG 48 oil with UV dye. Introduced just enough Freon to get compressor running, checked for leaks. Found leaks around the new dryer.
• Fixed leak as the O-rings that came with dryer were too large for the fitting. Replaced with smaller O-rings that fit on hoses into the dryer better. Why would the supplied O-rings be so large?
• Pulled vacuum again. Inserted a few more oz. of oil/dye, filled with 4 x 12 oz. (=1.36 Kg) cans of Freon with no other additives. Sticker on front of the frame says that the capacity is 1.4 Kg.
• Initially, was blowing cool air when this was performed as the sun was setting and the temperature was cooling.
• Now, when running during the past couple of days, the compressor cycles on and off for no more than 18 minutes when both left and right controls are set to LO. Blower speed set to max. Low humidity.
• Today, attached air conditioner gauges on the low side and high side. Initial readouts from gauges and scanning sensor values when the car started with an ambient temperature reported underneath the odometer at 67 degrees F:
o Low 38
o High 180
o 1 82
o 2 70
o 3 55
o 4 55
o 5 53
o 6 5
o 7 15
• When the compressor is running, it makes a “rumbling” sound that is louder than I recall it making in the past.
• Sixteen minutes later the ambient temperature is the same. The fans in front of the condenser cycle on and off. The vehicle is not moving. The compressor has run—as well as I can tell—continuously for 16 minutes. Readings:
o Low 36
o High 190 when the condenser fans are running
o High 240 when the condenser fans have stopped
o 1 80
o 2 70
o 3 57
o 4 57
o 5 56
o 6 81
o 7 13
• Referred to a 134a Freon table:
o 65 degrees F: Low: 25-35 psi High: 135-155 psi
o 70 degrees F: Low: 35-40 psi High: 145-160 psi
o As the ambient temperature is 67, the Low readings appear in the range, but the High readings are 30 psi too high when the condenser fans are running, and 80 psi too high when the condenser fans have stopped.
• Then the compressor turns off. It turns on for a few seconds a couple more times (left and right controls are still set to LO) but then stays off.
• After 18 minutes, the compressor will not turn on again.
• After 23 minutes, the compressor has not resumed running. The temperature of the air from interior vents no longer feels cool. Readings:
o Low 75
o High 90
o 1 84
o 2 70
o 3 77
o 4 77
o 5 77
o 6 86
o 7 05
• Questions:
o Could the rumbling sound in the compressor be a clue as to too much oil, not enough oil, or something else?
o Does the excessively high pressure imply a blockage?
o Should I have changed the expansion valve?
o Could I have too much Freon in the system?
o Any other tests to help diagnose why the compressor will not turn back on?
Thank you
• Have an ’94 S550 Coupe with 420K miles. Replaced compressor and expansion valve about 150K miles ago. Worked well until a month ago. Found dye on the bottom of hose from the compressor. No rear air conditioner unit.
• Replaced a leaking hose from the air conditioning compressor. Changed dryer. Pulled vacuum, inserted a few oz. of PAG 48 oil with UV dye. Introduced just enough Freon to get compressor running, checked for leaks. Found leaks around the new dryer.
• Fixed leak as the O-rings that came with dryer were too large for the fitting. Replaced with smaller O-rings that fit on hoses into the dryer better. Why would the supplied O-rings be so large?
• Pulled vacuum again. Inserted a few more oz. of oil/dye, filled with 4 x 12 oz. (=1.36 Kg) cans of Freon with no other additives. Sticker on front of the frame says that the capacity is 1.4 Kg.
• Initially, was blowing cool air when this was performed as the sun was setting and the temperature was cooling.
• Now, when running during the past couple of days, the compressor cycles on and off for no more than 18 minutes when both left and right controls are set to LO. Blower speed set to max. Low humidity.
• Today, attached air conditioner gauges on the low side and high side. Initial readouts from gauges and scanning sensor values when the car started with an ambient temperature reported underneath the odometer at 67 degrees F:
o Low 38
o High 180
o 1 82
o 2 70
o 3 55
o 4 55
o 5 53
o 6 5
o 7 15
• When the compressor is running, it makes a “rumbling” sound that is louder than I recall it making in the past.
• Sixteen minutes later the ambient temperature is the same. The fans in front of the condenser cycle on and off. The vehicle is not moving. The compressor has run—as well as I can tell—continuously for 16 minutes. Readings:
o Low 36
o High 190 when the condenser fans are running
o High 240 when the condenser fans have stopped
o 1 80
o 2 70
o 3 57
o 4 57
o 5 56
o 6 81
o 7 13
• Referred to a 134a Freon table:
o 65 degrees F: Low: 25-35 psi High: 135-155 psi
o 70 degrees F: Low: 35-40 psi High: 145-160 psi
o As the ambient temperature is 67, the Low readings appear in the range, but the High readings are 30 psi too high when the condenser fans are running, and 80 psi too high when the condenser fans have stopped.
• Then the compressor turns off. It turns on for a few seconds a couple more times (left and right controls are still set to LO) but then stays off.
• After 18 minutes, the compressor will not turn on again.
• After 23 minutes, the compressor has not resumed running. The temperature of the air from interior vents no longer feels cool. Readings:
o Low 75
o High 90
o 1 84
o 2 70
o 3 77
o 4 77
o 5 77
o 6 86
o 7 05
• Questions:
o Could the rumbling sound in the compressor be a clue as to too much oil, not enough oil, or something else?
o Does the excessively high pressure imply a blockage?
o Should I have changed the expansion valve?
o Could I have too much Freon in the system?
o Any other tests to help diagnose why the compressor will not turn back on?
Thank you