Quick and Easy RV Furnace Sail Switch Replacement

RV Furnace Repair

The other day I put my RV furnace repair technician hat on and discovered my RV furnace sail switch was the culprit. I’m pleased to say, it’s working again! Here’s how to replace your sail switch if yours dies too.

Late last spring, my furnace stopped working. It would come on, go through the initial 15-second startup phase, attempt to light then nothing. I did a bunch of reading about problems with RV furnaces and the most common problem I found that matched my furnace’s symptoms was an issue with the sail switch.

RV Furnace sail switch
Dometic/Attwood RV Furnace ModelAFDM25

What is a sail switch?

A sail switch has a tiny, yet very sensitive micro switch that senses when the fan is pushing air. The switch is there to prevent the furnace from firing if the battery is too low to run the fan at the correct speed or if the propane pressure is too low.

It is quite common for these switches to fail, particularly if they are excessively dirty or clogged with lint or pet hair.

Accumulated dust and spider webs.

Inspecting The Furnace

The first step was to take the cover off the furnace, switch off the reset/off switch, and clean the compartment really well. I also removed the sail switch and checked it for dust, lint, and beast hair. While the compartment was dusty and some lint had accumulated inside, it wasn’t bad at all. I used compressed air and a soft paintbrush to clean the compartment. The sail switch was clean as a whistle.

Testing After Cleaning

After cleaning the compartment, I reinstalled the old sail switch. Next, I went inside and turned the furnace up to 85 then back outside to see what would happen when I fried it up. The furnace blower came on, but it didn’t actually fire up.

On the circuit board, there is a fault light that helps you diagnose problems. The picture below shows Ignition Control Diagnostics near the bottom. I was getting one flash with a 3-second pause which corresponds with Air Flow/Limit Fault.

Help From 65,000 Friends

I consulted with 65,000 Airstream Addicts on Facebook and decided to order a new sail switch. Amazon to the rescue and only $23.

Two days later my new sail switch arrived and I opened the furnace compartment up to install it. I did my best to record and edit a video of the installation for you.

With my new sail switch installed and the furnace working again, I can move on to other repairs and maintenance.

You may also like, Does Your RV Need a Multistage Charge Controller?

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7 thoughts on “Quick and Easy RV Furnace Sail Switch Replacement”

  1. All the videos I could find for changing out the sail switch on our Airstream pointed to removing the shroud over the blower motor, and while not really difficult to do, I didn’t really want to dismantle the furnace to get to it. Then I found your post and the picture with the giant red arrow pointing to it, and it was JUST LIKE OUR FURNACE! Thanks for your post and sharing of knowledge!

    1. Thanks Stu! Fixing the furnace was much easier than editing the video. For my first video, I suppose it was ok. Hopefully my skills will improve as we go.

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