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"Four Button" Duo-Therm (Dometic) Thermostats

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It seems that for a number of years there have been problems with "Four Button" thermostats for Duo-Therm (Domestic) AC/heater systems. In retrospect, I have found that over the last 6--8 years, there have been numerous posts concerning this problem, but apparently I was totally oblivious to them, because I wasn't aware that there was a potential problem. Shame on me.

Apparently, over the last number of years, Dometic has changed the thermostats at least three times. The kicker is that that they apparently don't maintain any back parts, so that our only alternative is to not only change the thermostats, but to also change out the boards on the A/C units. At the cost of several hundreds of dollars.


I have found two places that, in an effort to respond to the market, are taking the old thermostats, reconditioning them, then taking your old thermostat and rebuilding it.

They are:

1. William Hendrix

william hendrix - Home


2. Frerichs Electronics LLC

Frerichs Electronics


I have no connection with either one of these companies. I only found them through avid research.

To be prudent, I suggest that you store this information in case you need it.

If you have a Five Button Thermostat beware. I believe that they are rapidly headed toward the same end.

Good luck, and good RVing.



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Thanks for sharing the information. We have not owned one of those thermostats but have read a great deal of problems with them. It has been a while since it came up on these forums but that probably don't mean that it is getting better.


I notice also that Freichs Electronics is also selling the ARPRV Control. In looking at the seller's site they seem to be under the price he sells them for. Do you know if those are rebuilt of something? The builder of the device is doing a seminar at Escapade and is going to be in the vendor area.


We had two of those pictured below and in 14 years did have to replace first one and then the other. And both were replaced under warranty in the first year we owned the RV.... These are still available and used in some new RVs. Sometimes newer is not better...


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We have one of those troublesome 4 button T-stats in our coach. When it starts to malfunction a bit, I carefully (emphasis on carefully) disassemble it and clean the contacts.


Got to be real careful though, as there's tiny springs inside and if they launch during disassembly they can be hard to find... :o


Good luck & safe travels :)

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Just to give closure to this thread, I ended up purchasing a re-built four-button thermostat from Mr. William Hendrix, a Certified Dometic technician from Erie, Colorado.


He sent it priority mail to me at the RV park I am staying in. I received it, followed his instructions to re-boot it. It worked fine, through all of the functions. I packed mine up in the box he sent to me, enclosed a check for $ 125.00, and mailed it back to him, post paid.


This was much cheaper than getting a five button or seven function "new" model because I didn't have to purchase the controllers for the units.


I am a Happy, but a little poorer, camper!




I wonder what the cost would have been if I had lived in Stick-and-Brick??

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We had the pleasure of stopping in at Mr. Hendrix's facility to have him replace our 4 button unit with one of his reman units last summer. Can't say enough good about him or the replacement unit he installed. Very personable fella & the unit is working well so far. Would not hesitate to recommend him for those of us with older units...

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