How to add a Thermostat to an RV Vent Fan
Need to keep your RV cool and ventilated? In this tutorial I’ll add an automotive radiator thermostat to an existing RV vent fan. Like a Maxxair Maxfan or Fan-tastic Roof Vent with a built in thermostat. It’s very easy to modify any any RV, camper, or trailer electric fan vent to add a thermostat to keep your rig cool and ventilated.
See the YouTube video.
This blog post is based on the transcript of the video.
Good morning everyone. I’m back in the camper for what I hope will be a short episode today.
Last summer I upgraded the batteries to lithium iron phosphate, added more solar panels on the roof, a bigger charge controller, inverter, and transfer switch. So now we can run a small portable air conditioner for a few hours when off grid or boon docking.
RV Vent Fan Thermostat
But, when we’re not in the camper I want to keep it cool and ventilated. And to do that I’ll need a thermostat controlled fan that will click on when it gets hot inside.
Unfortunately this RV didn’t come with one of those so, today I’m going the modify the existing fan and add this automotive radiator thermostat.
Well that’s the plan anyway. The fan that was already installed has a manual crank for opening and closing, a switch that turns the fan on with three speed settings, and that’s it. And there’s an override switch that turns it off when the vent is closed.
Existing RV Vent Fan
On the roof there’s a rain cover so it can be left open and vented. When not travelling anyway.
This thermostat is designed to turn on an automotive radiator fan when the coolant temperature reaches a set temperature on the dial. And the probe is meant to be installed (somehow) inside the radiator and immersed in the coolant.
Automotive Radiator Fan Thermostat
There’s three connector tabs on the unit. And I plan to wire it inline on the power wire between the existing speed selector and the lid power cut-off.
With an electrical meter I can turn the dial to the continuity setting and touch the probes to the tabs on the right. With the thermostat dial turned to minimum there’s no connection.
But when the dial is turned beyond the current temperature in this space then the meter turns to 1 indicating a connection is made and the fan will turn on.
And this thermostat can handle the current the fan will draw. That’s the main reason I chose a radiator cooling thermostat. So I would not need to trigger a relay with a lower amperage thermostat. I’m not an electrician but, this is what I understand.
And you can pick these up for about 20 bucks or so on amazon. Link in the description. Which is way way cheaper than replacing the fan with a model that has a thermostat built in.
RV Vent Thermostat Ideal Mounting Position
I’d like to mount the thermostat dial in the corner across from the speed dial but it might not fit, so I might need to instal it on the side of the plastic housing.
So let’s get this housing off and see what room we have.