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Greg Hunsicker · 10-07-2018, 11:28 AM

1999 Tradewinds 7370 300HP Cat on FL chassis. Dash a/c compressor would not come on and air only coming out of defrost vents. Connected gauges to the low side at rail below passenger and discovered no refrigerant pressure. Pulled vacuum it held then charged with 2.75lbs 134a per Evans tag on mixer box above generator. Waited an hour then started coach and turned on a/c then verified clutch pulled in and yay we are pumping refrigerant. I had the bedroom motor box propped up and after about 15 minutes KABOOM and a fog of refrigerant at very high pressure was discharging near compressor so I turned off the ac and before I could see exactly where it was coming from it quit dumping. I did not lose all the charge so I don't think a hose ruptured. So now I decide to figure out why the dash air controls are not working as should and discovered I had a blown fuse that feeds power to the vacuum pump and the condenser fan motor located left of the drivers seat. Replaced the fuse then unhooked the compressor clutch power wire then turned key to accy and turned a/c back on only to see new fuse arc and blow. Now I disconnected the vacuum pump power wire and unplugged the condenser fan motor. New fuse back in place and the fuse stays good when turning ac back on so now plug in the vacuum pump and it comes to life and all the dash air vents are now working perfectly. Turns out the condenser fan motor is stiff to turn so obviously it needs replaced which I can't find any numbers on it and the blade diameter is 15.5" and outer shroud is about 16.5". Anyone have any idea if there is a high pressure relief on the refrigeration system near the compressor? I am guessing no condenser airflow and hot water creeping into the mixing box hot water coil elevated the pressure to a dangerous level?

cfowler55 · 10-07-2018, 01:04 PM

Sorry I'm not familiar with your exact unit, however I have been doing auto and light truck a/c for many years. Almost all compressors do have a high pressure pop-off , typically screwed into the rear. It is normally protruding 1-2" and has a hex to install. A hole in the and where pressure is relieved. No air flow on condenser will cause high side pressure to be way over spec every time.