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Why is My RV Furnace Blowing Cold Air?

    Updated December 11, 2022

    This is a typical issue that many RV owners have previously encountered. No matter what brand of furnace or RV you possess, you will probably encounter this problem at some point. Your furnace may be spewing chilly air or abruptly turning off for a number of reasons. The most likely cause of this problem is that your sail switch is malfunctioning. This switch enables your gas valve to open, heating up your furnace as a result. You won’t have warm air blowing in your RV if there is anything wrong with your sail switch or something is preventing it from turning on.

    When the air coming from an RV furnace is chilly, there is a problem with the sail switch. A problem with the sail switch can prevent the furnace from lighting without stopping airflow, resulting in a gust of frigid air, whether it is low power supply or something obstructing the switch.

    Why Your RV Furnace May Be Blowing Cold Air

    You must identify the issue before you can resolve it. As already said, in order to start, function, and generate heat, your RV furnace needs fuel, electronics, and a number of sensors and relays. The most likely reasons and solutions for an RV furnace that is blowing chilly air are listed below.

    Sail Switch

    RV furnaces frequently fail to fully ignite, which results in them just blowing chilly air. The sail switch, a tiny, extremely sensitive switch, only activates when the furnace fan is running at full speed. Pet hair, dust, and debris from the RV’s interior, as well as debris that has been gathered and blasted around by the fan, might clog this switch.

    A fan motor not operating at full speed is a less frequent issue that could pass for a sail switch issue. As previously stated, the sail switch won’t operate until the fan is running at maximum speed. Sail switches are a regular problem and, for the most part, a cheap and simple fix, so many RVers opt to keep a spare on hand.

    Fuel source

    Let’s start with a statement that ought to be evident. Have you got gas? The gas valve will not light the furnace if there is no fuel present when it opens. There will be no flame heating the air; instead, your fan will be blowing chilly or room temperature air.

    Verify that you have propane first. Verify that the tank valve is open in the second step. Although it may seem obvious, we are all aware of how hurried we might be when putting our site together. There are many things happening, and occasionally small details are missed.

    Gas valve

    A gas valve opens when fuel is delivered to the furnace, allowing the gas to be lit and continue to burn. This cannot occur if the gas valve opens, resulting in a frigid air blowing from an RV furnace. You can hear the gas valve open when the furnace starts beginning. When it opens, a clicking sound will be heard. It’s probably opening if you hear this noise.

    A fuel obstruction could be present in a small aperture on the gas valve. It is possible to remove the orifice end and inspect it for debris. When turning on the furnace, there’s a chance you’ll hear the click even though the valve is still broken. If that’s the case, the valve needs to be taken out and tested using a 12-volt power supply. The valve should open when you connect a lead to its two lines, allowing you to blow air through it.


    Your furnace should produce a quick ticking sound as it attempts to start. This noise is the combustion chamber’s ignitor’s spark in action. A spark ignites the gas once it has been supplied to the chamber. If you don’t hear this rapid ticking, you should look into it more. When the furnace is attempting to start with the ignitor out of the combustion chamber but still attached (confirm that your gas is turned off), you ought to see a spark jumping between the ignitor tips.

    Look for cracks in the ceramic insulation visually. Verify that the space between the ignitor tips is as the manufacturer intended. Make sure the gas chamber is in good shape and doesn’t have any sizable gaps that could let gas escape before it ignites. The ignition module on the circuit board is most likely to be the issue if there is no spark or a very weak spark. The ignition module must be changed as a result.

    How Do I Clean My Furnace Sail Switch?

    Maintaining a clean RV furnace sails witch is crucial because any obstruction, dust, dirt, etc. can obstruct airflow, which affects how your furnace operates. Your unit may not have enough airflow if you’ve discovered that your furnace isn’t blowing warm air or that it randomly stops and starts. You should try to routinely clean your sail switch, or you might try to install a filter inside the device to stop buildup.

    If you follow the right procedure, cleaning your sail switch is rather straightforward. The switch inside your furnace must be found. Depending on the furnace model you have, this switch will be placed slightly differently; however, if you have a handbook, it should be simple for you to find the switch. Once you’ve found it, you can try to remove the sail switch to clean it or just clean it while it’s still in place. If the furnace in your RV is old and you’ve owned it for a long, now might be the time to completely replace the switch.

    You should be cautious about the cleaning agents you use on the switch because you are working with potentially dangerous electrical components. The best solution for anything that is firmly glued on is computer-grade compressed air. The ideal choice, though, would be a straightforward rag to remove any lingering dust. You should avoid using any form of liquid cleanser at all costs because it could endanger both the appliance and you.