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Why Is My RV Furnace Blowing Cold Air?

RV owners know that in some parts of the country, you might need heating and cooling in the same day. Fall, winter, and spring days can start a bit frigid, especially if you are used to warmer weather. Your RV furnace needs to be ready to go to start heating your RV when you need.

Having your furnace blow cold air is also a weird feeling. It’s supposed to be warm! Feels like what kind of a letdown, doesn’t it?

Cold air out of your otherwise potentially working furnace indicates an issues with lighting your furnace well enough to produce heat. You might also have a fan problem. We’ll talk more below.

Your RV Sail Switch

RV owners and home owners might be aware that in order to keep appliances like the furnace safe and usable, they have lots of measures in place. Sometimes these measures get confused or don’t quite work the way intended and make the best of a negative situation by producing less.

In this case, your sail switch might have an issue. The sail switch is designed to open once your furnace gets up to full speed and has the air flow needed to push air out of the combustible chamber.

If the sail switch doesn’t work, you get at best cold air. 

You get cold air because the fan is still working and circulating air that the RV furnace has pulled from the outside, but it’s not heated.

The sail switch is typically a lightweight, vertical metal or aluminum bar that moves up with the force of the fan blowing air.

The sail switch is typically on the back of your heater with one plug or wire running into it. The sail switch can be plugged by hair, debris, dirt or other junk. Blowing it out could readily help heat your RV right up.

If it doesn’t work, it’s also a very easy to replace part that often only requires four screws and a plugin. Cleaniing and replacing this part is as simple as some combination of a screwdriver, compressed air, or a paper towel.

One way to avoid an issue with the furnace sail switch is to clean it before it becomes a problem. Do you have pets or kids that bring dirt or hair into the RV constantly? Remove the sail switch once per year and give it a good cleaning. The switch is one of the easiest things to both go wrong and the easiest to maintain.

Gas Source

Ok, so this one is about as obvious as a tech support person asking if the computer is plugged in. You might be out of propane or fuel oil without knowing it. 

Check your propane tanks or whichever method you use to power your heater. A propane or LP tank will start to feel lighter and lighter, then run out.

Your furnace can still attempt to run without fuel, it just won’t do anything because it lacks combustible gas to actually create heat.

Gas Valve

Even with a good gas source, there are safety measures that keep gas from entering your furnace. The gas valve does this. You’ll hear your gas valve clicking to open and allow propane or other gas to enter.

If the gas valve doesn’t open or work, the gas won’t reach the combustion chamber and your furnace won’t provide heat. 

Replacing a gas valve is possible though it’s something you might want to call a professional for if you have no experience with gas pipes or DIY.


Your furnace has more moving parts to keep the gas burning. The ignitor is a plastic and metal piece that produces a spark to begin and sustain the combustion needed to heat your RV.

The ignitor can go bad. How will you know? The ignitor makes a ticking noise to indicate that it’s trying to start. If you don’t hear fast ticking, this could be the source of your problem. Without the ignitor, the furnace is not capable of using the gas brought in. You’ll get cold air instead.

The ignitor is fairly easily replaceable. Just make note of the part number on the item, or look up what model of ignitor works for your furnace. This is an instance when the part is “plug and play” and just requires you mount the ignitor and plug in various connections.

For safety’s sake

While we didn’t specifically mention this while discussing the variety of fixes your furnace might need – always turn the gas and electrical off to your furnace before making any repairs. The gasses brought to your furnace stay in the pipes because they are explosive. They are also often dangerous to humans when release in an uncontrolled way.

So turn off the main gas valve to your furnace or shut off your propane completely before doing any kind of maintenance to your furnace. You can turn these back on when you have changed something and want to test and see if it’s working.

If you don’t know how to turn the main gas valve off or the electrical, consult with a service technician instead.


A proper working furnace is a nice reassurance that when winter, fall, and even spring come, your RV will stay warm. Our suggestions will hopefully help you diagnose issues with your RV furnace. You might need some help actually fixing the problems presented by your RV depending on your own skills and the actual problem.

Furnaces also aren’t so scary. Some of the problems we mentioned above are actually safety switches that would prevent the furnace from causing a larger problem if they weren’t working right. Furnaces are not just designed to work, but are designed to keep the RV and home safe while working.

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