What Does That Button Do?

Buttons. Switches. Dials. Your coach has quite a few of them, seemingly placed everywhere and sometimes placed randomly. We have them on the front dash, hidden behind cabinet doors, on the walls of the coach, buried deep within the basement bays, and inside the engine and generator bays.

Some of these buttons, switches and dials remained a mystery to me for years. Over the next week or so, I will unravel a few of those mysteries. Some were relatively straightforward to decipher. Others not readily apparent. Consistent with the RV industry code of conduct, most were undocumented or left to the owner to figure out.

Today, we will start with an easy one. Ready?


That is the label found on one of our many dashboard rocker switches.

For years, this rocker switch was never touched. I knew it was there. But I never knew why it existed.

We have three sources of heat for our coach. We have heat pumps mounted on the roof, we have heated flooring and we have hydronic heat. The heat pumps and the floor heat operate with electricity. The hydronic heat consists of loops placed throughout the coach. These loops contain a fluid that gets heated by the Oasis boiler using diesel fuel. And fans behind the loops blow air into the cabin. The air passes through the heated loops and distributes the heat. I thought that all of the fans operated automatically. One fan does not.

The heat pumps and the floor heat would never warm the front entrance of the coach. But the hydronic heat will if a fan gets turned on.

The HYDRN HTR FAN HI OFF LOW rocker switch controls the hydronic heater fan located under the front dash. The hydronic heat would need to be selected on our Dometic thermostat and then the rocker switch can be used to turn the fan on or off.

The hydronic heat source is not identified as HYDRN or HYDRONIC on the Dometic thermostat. That would make things too easy for an RV owner. Rather it is labelled on the Dometic thermostat as “FURN” presumably short for “FURNACE”.

Note the letter “R” looks more like the letter “P” with a dangling right leg. Gotta love the obsolete technology that Dometic is using to control the interior climate of our coach.

They could install thermostats like this one but the RV industry is so slow to innovate and embrace current technology.


Another button to be demystified tomorrow.

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