Here’s Why Your RV Furnace Is Blowing Cold Air

Stop me if you’ve heard this one before: it’s an icy winter night in your RV, and you’re looking to warm up by your furnace. You go to turn it on, only to be greeted by a blast of freezing-cold air! What gives?

An RV furnace blowing cold air is a telltale sign of an issue with the furnace’s sail switch. Whether it’s low power voltage or something clogging the switch, an issue with the sail switch can stop the furnace from igniting without stopping airflow, resulting in a gust of cold air. 

In this article, I will be going over some of the mechanics of an RV furnace and explaining how those can result in your furnace blowing out cold air. Then, I’ll go over a few things you can look for and do to get your RV back to being warm and cozy for your next trip. In addition, there are two resources pages I made about Van life and Van build if you’re looking for more information.

Why Your RV Furnace Is Blowing Cold Air

To fully understand why your RV Furnace might be blowing cold hair, you’ll have to learn a few of the basic mechanisms behind your van’s furnace. And that has something to do with the sail switch in your heating systems.

What Is a Sail Switch, and What Does It Do?

A sail switch is a safety component used in different airflow and heating systems. Your RV furnace has a sail switch because a sail switch can avoid a potentially fatal fire hazard. The sail switch detects if enough air is blowing through the furnace before propane is released.

This prevents the furnace from igniting if there is not enough airflow to support it. Without the sail switch, the furnace would be prone to igniting without any proper airflow whatsoever, which could easily lead to the RV catching fire!

However, this configuration requires the sail switch to operate somewhat independently of the blower. 

Even when the sail switch is not set to release propane and ignite the furnace, the blower can keep working by itself. This results in—you guessed it!— the furnace blowing nothing but cold air.

Troubleshooting and Fixing Sail Switch Issues

Although knowing about the function of a sail switch will definitely help us start to figure out what’s causing your van’s furnace to blow cold air, it’s only really half the battle. If your sail switch is not activating when it should, there’s a myriad of issues that cause it—some involving the switch itself and some involving other pieces. Here are some of the most common issues that van owners will run into.

Low Power/Voltage Causes Unactivated Sail Switch

A van furnace emitting cold air could be the result of an inadequate power supply to the furnace blower.

An article by SuburbanRVParts points out that if your RV does not have an appropriate voltage, the blower wheel inside the furnace will be incapable of generating enough airflow to activate the sail switch. 

Increasing your RV power supply can vary depending on your exact situation; it could mean anything from upgrading your generator to getting more compatible electronic pieces for when you’re parked at an RV park. Either way, be sure to pay close attention to your van’s power supply and any safety precautions—you wouldn’t want to fry any of your electronic components!

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Dirt or Grime Can Obstruct a Sail Switch

If you haven’t cleaned your sail switch for some time, you might find that it isn’t functioning as well as it should.

If your sail switch has anything that could block it from being opened or closed, the furnace will not release propane and properly ignite. Examples of things that can block a sail switch include dirt, dust, mud, cobwebs, and insect nests. If you’re keeping a pet around your RV, their hair and fur can also get into the area directly behind the sail switch.

Keeping a constant eye on your RV’s furnace and regularly tidying up can help avoid this problem. If your van’s furnace is blowing cold air, it could be that something has dirtied your sail switch and is preventing it from doing its job!

The video below from My RV Works, Inc. on YouTube shows the process of checking and cleaning a dirty sail switch of a furnace. I recommend giving it a watch to get a grasp on what you should be looking for if you think something might be blocking your switch!

Your Sail Switch May Be Damaged

If you’ve thoroughly examined the furnace of your van and are still unable to find anything visibly wrong with the furnace, it is possible that your sail switch might be damaged. This can be the case sometimes with older, more run-down RVs. 

Blowing cold air isn’t the worst thing that a damaged sail switch can do; remember, the switch’s main purpose is preventing potential fire hazards from occurring. If you have any suspicion that your sail switch may be damaged, replacing it as soon as possible is imperative for your safety.

Thankfully, it’s relatively easy to find a replacement sail switch out on the market. You’ll have to do some digging to find the exact one that will fit with your van, but to get you started, why not check out this Atwood 36680 Sail Switch on It’s built specifically for RVs and campers and fits a wide range of different models of vans.

Another good sail switch option worth looking at is the Suburban 232261 Sail Switch from This sail switch works well with the furnaces like the SF-30F and SF-35FQ furnaces and many others. The product has also received high ratings from happy and satisfied customers.

Final Thoughts

If your RV’s furnace is blowing cold air, the root issue likely has something to do with the sail switch—a key component to keeping the van safe and sound. If the sail switch is not activating for whatever reason, the furnace of your vehicle will continue only to route cold air throughout your RV. 

Thoroughly investigating both the switch and the furnace is the key to fixing your furnace and protecting yourself from any danger that might arise.

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