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brhargiss · 05-08-2022, 08:49 PM

Have a 1997 Newmar Mountain Aire 40 foot coach. Been plugged into shore power, cleaning the coach for a trip next week and cannot use a/c's. No power at the on/off switch. Have power to all outlets, microwave and refrigerator working also. Checked breakers, nothing tripped. Reset all breakers in panel, just in case, but to no avail. Must be missing something, but WHAT???

HarryStone · 05-08-2022, 09:25 PM

Your AC's need 12 VDC as well as 120 VAC to operate.

jrollf · 05-09-2022, 05:58 AM

Check that your battery cutoff switch is "on" when plugged into shore power (this is also how your battery gets charged).

brhargiss · 05-11-2022, 06:12 AM

Thanks for your input on my situation. Found there was one (1) battery that needed to be replaced, but still did not fix the problem. The cutoff switch has been reset as well as all breakers in breaker box. All lights, fans, refrigerator, microwave and wall plugs have electric to them. But no electric to the Duo-Therm switch for ac's/furnace. Any more suggestions? Thanks again, Bill

bddadles · 05-11-2022, 08:48 AM

Long shot but is the thermostat turned on? If individual zones are the setting correct?

bentjm · 05-11-2022, 08:59 AM

You have to have 12v up to the AC unit. Look at the 12v fuse panel above your toilet. There is a 12v fuse for the AC there.

Skip426 · 05-11-2022, 09:22 AM

Is your Duo Therm thermostat a four button unit ?

My 99 DS has two inline fuses for power to the thermostat , hanging behind the furnace return air grill .

Note this is not a location cast in stone , as other DS owners have found these fuses behind the outside furnace service panel .

Pictures taken with return air grill removed ; it's held in place with Velcro .

Lv2Roam2 · 05-11-2022, 09:29 AM

At this point I'd suspect the t-stat ... might try a 12V system reset with the t-stat turned on either by unplugging the t-stat power wire or shutting down the entire 12V system for about 10 minutes ...

DandyDon · 05-12-2022, 01:13 PM

Had a similar problem this spring except my thermostat would light up normally and show temp readings etc but the ac would not respond at all. I have a 5 position DuoTherm thermostat and you reset it by holding in the top and bottom buttons, zone and mode at the same time. If it resets you'll get a digital readout saying FF. If that happens you're good to go.

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brhargiss · 05-21-2022, 08:51 AM

Thanks for all the hints and suggestions for the fix to my a/c problem. Found that the circuit board in the controlling a/c needed to be replace. Naturally, the board I needed was made by a company that has gone out of business and the replacement aftermarket board went extinct two years ago. Was able to find a used board and thermostat like mine that fixed the problem. Again, I appreciate all the help. Bill