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DesertLass · 02-13-2017, 09:54 PM

We have a 1998 National Dolphin. We've had a few toastier days lately, and in the next 30 it will get very warm here in Arizona. We tried to run our AC to see if it works, but the thermostat won't light up, there seems to be no power to it at all. Is there a switch somewhere? Not sure if it's the thermostat we need to replace, or if there is a hidden switch to get it to work. It's a Dometic duo therm with four buttons. We only have one limited manual for the rig, and nothing about the systems on board. Thanks for any help.

GraySeal65 · 02-14-2017, 06:20 AM

The 4 button Dometics were known for failing switches. They are obsolete to, there is a write up on how to rebuild them on the net somewhere, (easy to do with basic hand tools) I have to leave for work so if I can find a link I will post ASAP.

Found it. http://www.beamalarm.com/Documents/d...er_repair.html

DesertLass · 02-15-2017, 12:00 AM

Thank you SO much for the info!

I'll keep the link up to show my Dear David tomorrow morning. Sheesh, what a pain! We kept thinking there had to be a switch somewhere to activate it. We were so wrong.

DesertLass · 02-16-2017, 10:06 PM

So this is what we did. An RV tech told us that those Dometic thermostats are obsolete, and that the best way to handle this was to bypass the ducted AC and just install those single control AC units. I found them on ebay, and for two of these units it only cost me $132. Problem solved with the AC, he will install them for us when they arrive.

Since we spend most of our time in Arizona, the ceiling ducts will be extremely inefficient when it gets hot. That ceiling could be well over 150 degrees, and pushing the AC air through those ducts would result in "not very cold AC" for us. I'm so happy we called him, because he said those thermostats are total junk, and unnecessary.