Forum Discussion

Rbertalotto's avatar
Rbertalotto
Explorer
Jun 05, 2016

Adding thermostat to roof top AC modification

My toy hauler, Forest River 19rr has a simple roof top AC unit. It does not have a thermostat . Low-Med-High is the only cooling controls.
Can I simply install a digital thermostat that triggers a relay to cycle this AC unit on and off by simply interrupting the 120v feeding the unit?
Would turning the unit in and off in this manner damage the unit?
  • It can be done but it is not easy. I did it to one of my other trailers and honestly I would not do it again.
  • It won't hurt anything. There is the possibility of short cycling, but that's no different than the mechanical switch.
    For a simple on off relay, you don't need to put it in the air conditioner, you can put it at the breaker panel.
    I am interested in the make and model of the air- I've never seen one with no thermostat at all.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Toddupton wrote:
    It can be done but it is not easy. I did it to one of my other trailers and honestly I would not do it again.


    It might just be easier than you think if you can find a good spot to do it.. Two spots come to mind,, One is the breaker panel, the other end of that wire is the A/C.. a LINE VOLTAGE Thermostat.. These come in heat, cool, or heat/cool types. I have two of them, one came with screw terminals on a Micro-Switch (3 Terminals, one for heat, one cool one common) the other with a cord and Plug/socket.

    The linked page shows some examples.. Mine are for heaters. One I added to a heater that had none.. The other the built in electronics failed so I added the plug in model.

    The only thing I do not like about these I do not like is this.. Running an A/C with the fan on HIGH you quickly become "immune" to the noise as it were.. But cycling the entire unit on and off it's very annoying.. So if you can find a way to break out power ONLY to the compressor.. that is the way to do it.. The honeywell I used on the heater can do that.

    Though the Honeywell is "Surface mount" the microswich sticks out the back and needs to be "Recessed" into the unit.. Which for me, was ideal.. That may or may not for you.

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,191 PostsLatest Activity: Jan 19, 2025