Author Topic: Duo-therm AC Replacement  (Read 1814 times)

jeffprupis

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Duo-therm AC Replacement
« on: July 30, 2021, 07:59:43 PM »
Our front AC seems to be dead. When switched on, it struggles to start and then pops the circuit breaker. Repair facility thinks (haven't brought coach in yet) it's the compressor and will need to be replaced (ouch). Can the compressor be replaced? Will I need to replace both units? Thanks

David T. Richelderfer

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Re: Duo-therm AC Replacement
« Reply #1 on: July 30, 2021, 08:25:30 PM »
When our center roof AC/heat pump had the same problem several years ago, we had it replaced.  Our three ACs are Penguin II cooling and heating units.  The cost for the new unit was about $1,600 plus a wiring modification to allow it to be controlled from the bedroom thermostat.  The whole new unit with the wiring change was $1,800 to $1,900.  The bedroom thermostat in our coach controls both the bathroom (zone 2) and bedroom (zone 3) AC/heat pump units, thus the wiring modification requirement.  I was advised these are throw-away units when they quit functioning, especially after ten plus years of use.
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Richard Davis

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Re: Duo-therm AC Replacement
« Reply #2 on: July 30, 2021, 08:29:51 PM »
I "assume" you have the Dometic brand roof-top air units.  Before you spend lots of money on those old units, spend a little money and replace the capacitor(s).  There are a few available on-line (I ordered one from Amazon last week).  But, repair parts are quite scarce and new units are almost impossible to find, so be quick.  If it is actually the compressor and not just a failing capacitor, it is probably not cost effective to repair.  If your units are original, they have exceeded their life expectancy.  But, as I commented above, finding new ones is difficult at the moment with shipping and supply line disruptions due to the pandemic. 
Good luck.
Richard
06 Monterey Ventura IV, C9 400 hp

Joel Ashley

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Re: Duo-therm AC Replacement
« Reply #3 on: July 30, 2021, 09:54:19 PM »
The most common AC issues are caused by a low voltage source, all too often the result of a voltage drop across too long and/or too small a gauge extension cord, or an overloaded older RV park’s electrical grid.

First thing is to determine the faulty part.  If it’s just a start capacitor (there’s two, start and run) that’s lucky and certainly less costly than having to replace that AC plus the rear one;  since today’s AC’s don’t mesh well with the original Duo-therm thermostats, it’s common for owners to end up replacing both roof units and the thermostats… obviously not a cheap fix.

There are several troubleshooting videos on You Tube, and you might check some out.  Try the one by “My RV Works, Inc.” in Port Angela’s, WA… “Diagnosing An RV Air Conditioner That’s Not Cooling”;  a bit talkative but thorough.  Also is one by “RV Tech Tips”, “Dometic AC that won’t start. How to replace a start capacitor”, among many others that may or may not be relevant to your model, and that aren’t all particularly well done.  Also check out:  https://www.doityourselfrv.com/rv-ac-repair/   .

Our Duo-therms may be before Dometic bought in, but the principles are the same.  Just be careful on the roof and be sure to discharge capacitors before messing with them.  If you don’t opt to do the test yourself, watching the videos will at least give you an advantage when discussing the issue with techs.

Joel
« Last Edit: July 30, 2021, 10:05:45 PM by Joel Ashley »
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Fred Brooks

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Re: Duo-therm AC Replacement
« Reply #4 on: July 31, 2021, 02:09:21 AM »
   Jeff,
 If you have an analog amp probe you can perform the following test. Unplug your coach from shore power. Remove the cover on the circuit breaker box. Locate the black wire that goes to the air conditioner circuit breaker. Reroute the wire just enough to get the amp clamp meter around the wire. Plug the coach back in and have someone turn the air conditioner. The meter should momentarily jump to 50 amps and then settle back at 12 amps (if 80 degrees ambient temperature) Anything above 15 amps indicates one of the components is laboring which is probably the compressor. You can try replacing the start capacitor for the compressor with one of those "boost capacitors" that give the compressor a jolt to get it going. Regardless the unit has reached its life expectancy so be prepared to replace it. Be patient because there are no air conditioners available presently because demand has exceeded supply. Fred
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