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Topic: Testing resistance of PTCR for Dometic Duo Therm AC (Read 3815 times) previous topic - next topic

Testing resistance of PTCR for Dometic Duo Therm AC

My front air conditioner, blows air, but it's not cooling. The rear air conditioner works fine. I tested the capacitors and the compressor side capacitor is shot. The fan half of that capacitor is good. How do I test the PTCR relay? When I search for information on the Internet, the answers are for refrigerator relays. I'm measuring 42 ohms at room temperature on the PTCR, is that in range or too high?

The Phillips capacitor that was in series with the PTCR tested good.

1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.

Re: Testing resistance of PTCR for Dometic Duo Therm AC

Reply #1 –
The PCTR is not a relay, it is a big resistor that increases resistance as it heats up with current flowing thru it to the compressor.  Doubtful it went bad.  Replace your cap and you should be good to go assuming your compressor is working.
Jerre and Kathy Griffin
2003 U320 4220 Special
Build # 6207
2022 RAM Laramie 4X4 EcoDiesel
2002 Country Coach Magna 37 Tag- Forever Coach-Died in fire 7/23
1997 Country Coach 32 Intrigue-No slides-Wonderful

Re: Testing resistance of PTCR for Dometic Duo Therm AC

Reply #2 –
I changed my run capacitors on both mine which solved the issues. Ice cold air now
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox
 

Re: Testing resistance of PTCR for Dometic Duo Therm AC

Reply #3 –
Reused the PTCR resistor and unit now running and cooling. Hopefully nursing these 25 year old units for another season. Following the replacement options thread with interest.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.