06-17-2015, 07:17 AM
Gordon: yes I would appreciate the information you have, it would simplify my research.
To the others that have noted that the refrigerant is low. I seem to own the mystery coach so nothing is as straightforward as it seems. The symptoms of plugged capillaries are similar to low refrigerant and tend to confuse the issue. In these small simple systems I have it is possible for all the refrigerant to condense as liquid and be held in the condenser. The liquid pressure (130ish) we measured is consistent with R22 at the prevailing temperature of the condenser at the time (68ish). The vacuum on the vapor side is an indication that a restriction MAY exist, though it could also be the result of a low refrigerant charge. The judgement of the tech was that the vapor side pressure was far lower than any low charge condition he had experienced. In addition, if the charge was low the cooling cycle would still be happening though at a much reduced amount. We could detect no cooling at all happening in the capillaries or the adjacent evaporator tubes. The belief is that with 130ish pressure on the liquid and a vacuum on the vapor side we would be able to detect some cooling if the charge was circulating.
There is one more test we will conduct prior to opening the system and trying to blow it out backwards (a 50-50 probability of success according to the service manager). The test involves monitoring the speed of pressure drop-off on the liquid side once it is pressurized and then shutting off the compressor. If it drops off fairly quickly (we may need to compare to a normally operating system) either the compressor is leaking backwards (thought to be unlikely since it pulls a strong vacuum) or the capillaries are open (and we then add refrigerant) or if it drops really slowly then the capillaries are essentially blocked and we proceed to attempt blowing out the blockage. Honestly, I'm hoping it's just a low charge, but I'm not counting on it. I'll let you know what we find.
To the others that have noted that the refrigerant is low. I seem to own the mystery coach so nothing is as straightforward as it seems. The symptoms of plugged capillaries are similar to low refrigerant and tend to confuse the issue. In these small simple systems I have it is possible for all the refrigerant to condense as liquid and be held in the condenser. The liquid pressure (130ish) we measured is consistent with R22 at the prevailing temperature of the condenser at the time (68ish). The vacuum on the vapor side is an indication that a restriction MAY exist, though it could also be the result of a low refrigerant charge. The judgement of the tech was that the vapor side pressure was far lower than any low charge condition he had experienced. In addition, if the charge was low the cooling cycle would still be happening though at a much reduced amount. We could detect no cooling at all happening in the capillaries or the adjacent evaporator tubes. The belief is that with 130ish pressure on the liquid and a vacuum on the vapor side we would be able to detect some cooling if the charge was circulating.
There is one more test we will conduct prior to opening the system and trying to blow it out backwards (a 50-50 probability of success according to the service manager). The test involves monitoring the speed of pressure drop-off on the liquid side once it is pressurized and then shutting off the compressor. If it drops off fairly quickly (we may need to compare to a normally operating system) either the compressor is leaking backwards (thought to be unlikely since it pulls a strong vacuum) or the capillaries are open (and we then add refrigerant) or if it drops really slowly then the capillaries are essentially blocked and we proceed to attempt blowing out the blockage. Honestly, I'm hoping it's just a low charge, but I'm not counting on it. I'll let you know what we find.
Jon Kabbe
1993 coach 337 with Civic towed