Heating, Air Conditioning, Fridge, HVAC/A/C Compressor Thermal Shutdown


I recently had my A/C compressor replaced.  Prior to the replacement, the compressor would shut off and I would have no cooling.  If I squirted the compressor with water, it would come back on and work for a while. It would also work ok at night, when the outside temps are lower.  The repair person said that the compressor is old (11 years) and needs to be replaced, so I did. That cost ~$1200.  The new compressor does exactly the same thing I described(thermal shutdown).  Now, when that happens, I squirt the FINS with water (from garden hose) and the compressor comes back on.  The repair guy came back.  He measured the air temp coming in (over the fins) and out the top of the fan. He said the delta should be 30 deg F. and mine is 15 deg.  Now he says this is the problem-the unit is not removing enough head from the refrigerant so the refrigerant is too hot, causing the compressor to thermally shutdown.  The fins are not dirty, but I cleaned them with fin cleaner. It did not make a difference.  The fins look to be in decent shape.  There is maybe 5-10% that I would say are deformed but they look pretty good.  It is a wide open area around the unit - no bushes, weeds, etc.

The compressor draws around 15 amps when running and has a rating of 19.8 amps. I monitored it over time, and it never gets close to 19.

This is an R22 system, so the repair person removed the original coolant and topped it up when he did the compressor replacement.

Does his assessment sound correct?  If so, he screwed up with the original recommendation to replace the compressor.  Could it be something else?  What about the refrigerant itself?  Does it become less efficient at transferring heat as it gets old?  Any other ideas?  The new compressor is a bristol 3.5 ton (H22J383ABGA).  1 lb of new R-22 was added.  Superheat at 20 deg and sub-co0ling @ 10 deg.  The fan is working fine. The superCAP was replaced ~ 6 months ago when the fan would not turn on. The capacitor was bad.

The condenser unit is a York H1RA042S06D

Thank you.

There are several issues that can cause a compressor to trip out on high temp.  The refrigerant charge can be an issue, but the refrigerant itself does not go bad or need to be replaced due to age.  Though you sent me some temperature readings, it is not enough for me to determine if the unit is running ok.  Age can also be a factor, but the readings would tell me if there is a problem.  I would not replace a compressor that is running due to age without knowing how the unit is running.  I have seen compressors last for 20-30 years without an issue.  The fact that you are still having the problem leads me to think the compressor may not have been the issue.  


Heating, Air Conditioning, Fridge, HVAC

All Answers

Answers by Expert:

Ask Experts


Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

©2016 About.com. All rights reserved.