Dometic HVAC issues...can't find anyone to correct the problem...PLEASE HELP!


Old 11-10-11, 07:25 AM
Thread Starter
Join Date: Nov 2011
Location: USA
Posts: 2
Dometic HVAC issues...can't find anyone to correct the problem...PLEASE HELP!

Briefly, we have a 2008 Holiday Rambler Admiral with dual Brisk Air heat pumps and a gas furnace run through a SINGLE Duo-therm 5 button CCC 3109228.019. We were at a campground hooked to 30 amp service, we left for a few hours with only front A/C running and more than likely had several voltage drops from to many units, but upon our return the front A/C was not working. Service guy came and replaced fan motor and control box.

Since that time, HVAC will not cycle on and off properly.

FRONT UNIT: In A/C mode, unit will turn on when thermostat is turned below 70 deg, will run and cool properly BUT not turn off until you manually raise the CCC to 72 degrees, even when temperature setting has been reached or bypassed! Then unit shuts off almost immediately. In Heat mode, basically just the opposite happens, you must set the CCC to 72 or above to turn on, unit will run and heat normally, but never turn off until the setting on CCC is manually changed to 70 degrees, even if temperature reached 85 degrees! Same thing happens with furnace, with one exception…the furnace burner will cycle on and off, but fan will never stop until you manually reduce thermostat setting to 70 deg. Then fan runs in proper cool down mode for a minute or so and then shuts off.

REAR UNIT: The rear Heat and A/C operates semi-normally! By-the-way, it was turned off during the low voltage incident! The unit seems to function normally, except that it also has a “temperature number that it likes!” What I mean is, it will function in HEAT MODE if you set the thermostat to 76 degrees or warmer (the thermostat reads 3-4 degrees warmer than it actually is!). It will run, heat and cut-off properly! BUT, if you set the CCC to 73 degrees, it will never turn on! ALSO, if the front HEAT is running and you then set the rear unit to run, it will not turn on until you raise the setting to 80 degrees or more!

Please understand that while I am not a HVAC person (although I have now learned way more than I ever cared to know!), I am a mechanical engineer. We have used temp probes to verify that requested temp is either less or more than ask for. Our rear remote sensor has always been about 3-4 degrees warmer than front.

This is a list of what has been tried:

Three new thermostats have been tried…with no change to problem!
12 DC current is correct to thermostat (12.50v) and CCC (11.41v)
Run capacitors exchanged, front to rear…no change to operation
Original control board was tried…functioned same as new one. Rear control board was moved to front unit…no correction to problem
Another new control board was purchased and installed w/new thermostat and they did nothing to correct the issues.
Wiring traced…appears correct
Replacement fan is correct part number
Control boards are correct numbers 3109226.005
No shorts appear in 12 volt wiring to thermostat
Remote sensor ohms correct
Each time any change was made the CCC was reprogrammed

Did not replace start capacitor or PTCR…was not sure if they might affect fan operation

The initial service tech never came back. The local dealer where we were contacted Dometic and they said it was a CCC issue, hence first new CCC! We have since had to come to Texas and I contacted two local mobile repairmen and BOTH said it had to be thermostat, so I went to local dealer and talked to Service Manager. He confirmed it had to be thermostat! Hence second CCC. Needless to say, it don’t work! Purchased another the new control board and new thermostat and it did nothing to correct!

Anyone have a fix? Suggestion?
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Old 11-15-11, 11:16 PM
Join Date: Jan 2006
Location: Ontario, Canada
Posts: 759
Not sure if you have access to these but will give you a link for troubleshooting manuals for 4 and 5 button CCC systems. Being your background should allow you to follow these and hopefully pinpoint the trouble. Good Luck, and if all else fails, have you tried calling dometic direct and asking for possibility of them having a troubleshooter available in your area, and explain what has been done and the mounting cost to you ? Here's the link. Scroll down to air conditioner and heat pump service and download applicable manual(s).
( Service Documents )
Old 11-16-11, 06:15 AM
Thread Starter
Join Date: Nov 2011
Location: USA
Posts: 2
Thank you for the reply, Mike! I had the manuals and Dometic would NOT talk to me because I was not a tech! Seems like a poor way to run a business that depends so heavily on consumers. I did finally locate the problem. The original tech had put a screw through the ambient sensor wire! Two other techs and two dealers later...

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