There’s a switch hiding in your furnace that could cost you $200 to push!

By Andrew Herrick
In my career as an RV-engineer-turned-RV-technician, I have discovered the existence of a hitherto unknown $200 switch. It looks like a simple $5 rocker switch, but beware! If you pay someone to push it, it could cost you two Franklins.

Now, before you mutter to yourself, “I don’t understand furnaces and switches and electrical thingamajigs” and click through to the next RVtravel.com reader poll … wait a second! I promise you don’t need a multimeter to understand this article, and I cross my heart I won’t use the word “amperage” even once. In fact, you are exactly who should be reading this post.

“Where do I find this $200 switch?”

First question: Where is this switch? Well, if you remove the exterior access cover (if your RV manufacturer was kind enough to provide you with one) from your RV gas-fired appliance, you may find an on/off rocker switch buried in the circuitry. It might look like this:

Here are a few quick things to know about these inline RV furnace switches:

• They are often found on furnaces and water heaters. For example, they are common on Dometic, Atwood, and Suburban LP furnaces and almost all tankless water heaters.
• They are mounted in different locations, sometimes inside the sheet metal shroud, and sometimes outside. If buried within, they can usually be spotted through the return air grate.
• In some furnaces, the toggle switch also doubles as an inline circuit breaker.
• Sometimes these switches shut off power to the appliance; sometimes they shut off power to the thermostat.
• Not all gas-fired appliances have these resettable switches. In my experience, the older the RV, the more rare they seem to be.

“What’s the purpose of this hidden RV furnace switch?”

“Why,” you may wonder, “is there an on/off switch on the OUTSIDE of my RV?!”

It’s not for you, the customer. It’s for me, the service technician. Usually, the rocker switch is a safety feature that allows me to shut off 12V power to the appliance or the master thermostat when I’m diagnosing and testing. Without 12V power, the control board can no longer “think,” and the appliance shuts down. This de-energizes the gas valve, which cuts off the flow of propane vapor and resets any lockout faults. All safe!

“There’s no way this little switch costs $200!”

So, why does this small, insignificant RV furnace switch cost $200?

I have driven to numerous service calls where the furnace didn’t work, the thermostat was dead, the air conditioner wouldn’t turn on, or the hot water was coming out cold—and the felon was this simple switch. I flipped the latch, and the appliance came alive. “Now, will that be cash, check, or card?”

These switches (usually) don’t flip themselves. Most of the time, the RV was recently purchased or serviced; someone else had tripped the switch and forgotten to reset it, and the frustrated customer was left to figure it out alone. Sometimes, the switch was accidentally flipped. Once, a customer of mine had recently replaced the sail switch in his own furnace. The next weekend, his furnace AND his thermostat were dead. The culprit? The little power switch! He didn’t even realize he had one, let alone that he had accidentally pushed it.

That’s really all there is to know. If you have a non-responsive gas-fired RV appliance, look for the switch. It’s like the Call-Before-You-Dig campaign: Flip Before You Call! You just might save yourself $200.

##RVT1190