We have 2 original Duo-Therm Penguin A/C units in our ducted ceiling (1997 U-270) that have worked flawlessly until last night. The forward unit was on and at 2:30am there was a faint burning smell and Watchdog power management shut off power to the coach with a high amperage draw fault in line 2. I reset the coach power at the pedestal and it tripped again immediately when the A/C started. Another pedestal reset and after turning off the breaker to the forward A/C everything but the front A/C is normal.
Removing the cover of the A/C on the roof there was a faint burned smell but I don't see any obvious burned wiring, no blown fuse on the board, or other issues I could see. The fan turns by hand ok and if I set the front A/C to fan only it works. Everything is clean as we serviced a month ago (and every year). My suspicions are a bad capacitor (run or start) or possibly a bad PTCR device. I hope it's not a bad compressor - it trips the pedestal under very high load as soon as the A/C starts the fan on startup...the compressor should be on a delay (think that is the role of the PTCR) and the working unit (and until now this bad unit) normally starts maybe 80 seconds after the fan starts. Why would there be a very high load within seconds of powering on the AC if the fan runs fine by itself and the compressor is delayed (if that is the case now)?
I am going to test both the capacitors (safely discharged first) with my Fluke MM. What else should I test? If I find no faults should I just replace both capacitors and maybe the PTCR? Finally, if I cant fix this older unit should I replace it with a new unit? We have the 4 button thermostat....is any Dometic compatible? I am sure many have been down this road and with 103f predicted next week in Killeen Tx it's tempting to just buy a new front A/C with it's own additional thermostat from PPL (we can drive there). Any advice appreciated.
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Update: The START capacitor has yellow powder residue on the top and looks like it has maybe been overloaded (slight smell of burned plastic also). It is a plastic Phillips 88-108 mF unit and it does measure at 106-107 (just within spec). The PTCR has continuity though it has a slight burn mark on the outside casing as well. My plan is to get a new START capacitor and see if that is the issue. I will post results. The jury is out on this repair!
Another Update+++++++++++++
Replaced both capacitors (easy job). Tried it again and this time the fan started normally and then the compressor started for about 2 seconds and smoke started shooting out the PTCR device and it got red/white hot. I was on the roof looking so had wife shut it down ASAP. Probably a bad compressor. All compressor checks were ok except the OHMs don't balance indicating higher resistance on the START winding (Common to Run=1.3 +Common to Start=6.7=8 total however Run to Start = 7.4 which indicated possible high resistance in the RUN winding. Trying to get another PTCR for a final test. If this one goes up in smoke....getting all new A/C Penguin II and new thermostat.