Last updated on October 30th, 2023 at 06:27 am
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When we travel in our RVs during the winter, we’re usually trying to enjoy snow, late-night campfires, and a ton of fun adventures, not necessarily the cold itself! Getting cold in an RV can be uncomfortable and cause problems for RVs such as freezing pipes. Luckily, your RV’s furnace is designed to help combat this and keep both you and your rig warm during winter weather.
But what should you do if an RV furnace is blowing cold air?
The most common cause of a furnace blowing cold air is an issue with the sail switch. When there is a problem with the sail switch, the furnace is unable to ignite and blows cold air instead. Lack of fuel, problems with the ignition itself, or the furnace’s power source can also cause this issue.
Let’s dive into each of these reasons and why they can cause problems for your furnace.
4 Reasons Why An RV Furnace Is Blowing Cold Air
RVs are fantastic rigs that allow us to travel extensively with the comforts of home. Staying warm is a key part of RVing, especially during the colder months, but what do you do if your RV furnace is blowing cold air?
There are a few different reasons for an RV furnace not working as it should. Chances are, with a little troubleshooting, you’ll be able to diagnose your furnace issues and get cozy in no time!
Reason 1: Sail Switch
Sail switches are found in many different heating appliances, from stoves and furnaces to heaters, and they all serve the same purpose. They detect the movement of air through the furnace and can also detect if liquid is present prior to ignition which has a major role in fire prevention.
When an RV furnace is blowing cold air, the sail switch may be the cause of the problem. The sail switch may be damaged, which is often just the result of common wear and tear, as discussed in the video below:
If this is the cause, it’s time for a new switch! Sail switches can also stop working if they become blocked with dust, dirt, or pet fur. Cleaning the switch should resolve this issue, and keeping it clean in the future will help prevent further RV furnace problems.
Lack of power can also be the cause of a sail switch not working, so if your rig isn’t getting the voltage it needs, both the sail switch and even the blower itself in the furnace likely won’t run properly.
Reason 2: No Fuel
It may seem obvious, but with so much going on at the campground, it can be easy to forget about gas. If you’ve run out of propane, the furnace won’t be able to ignite and will therefore be unable to produce any warm air. Thankfully, this is a simple fix, and you likely won’t forget to get propane again!
Reason 3: Ignitor
Problems with the ignitor can also be the cause of an RV furnace blowing cold air. In propane and other gas furnaces, the air is heated by gas that’s sent to the combustion chamber and ignited by a spark. To know if the problem is with the ignitor simply start up your furnace. If you hear a ticking sound in the beginning, then you’re good to go!
If not, then you know the ignitor isn’t working.
It’s then wise to check both the ignitor and the gas chamber of the furnace. Check the gas chamber for cracks as this can be a reason for gas escaping and failing to be ignited. It’s a good idea to also check the furnace’s insulation for the same reasons. Damage to the insulation or gas chamber will need to be fixed, or the furnace replaced.
Reason 4: Propane
An RV furnace that uses propane to produce heat can have a few specific problems resulting in cold air being blown through instead of hot. Camping during extremely low temperatures, well below freezing point, can make propane more vulnerable. Often, it will begin to liquefy in the extreme cold and this means there’s no gas to be ignited.
Additionally, the newly added moisture in the furnace may cause different parts like the valve or regulator to freeze. It’s a good idea to have electric heaters on hand or a generator-powered backup if you have a propane furnace in case the worst happens and there’s no gas for the furnace!
2 Reasons Why An RV Furnace Is Blowing Lukewarm Air
So, your RV furnace isn’t blowing cold air, but it isn’t blowing hot air either! If you’ve got an RV furnace that’s blowing lukewarm air, there are a few likely culprits. It’s worth trying to get to the bottom of the problem sooner rather than later as a cold RV when temperatures drop isn’t fun.
Thermostat
Occasionally, the cause of a problem can be really simple, and if you’ve got an RV furnace blowing lukewarm air, it may just be the thermostat. Your RV’s thermostat has two different modes it can be set to when it’s running; ‘On’ and ‘Auto’.
Ideally, the thermostat should be set on auto as it then uses an array of sensors to blow hot air when the RV reaches an indicated temperature. If the thermostat is set to the ‘on’ position, the furnace won’t know when to make this distinction and may not always blow warm air.
Dirty Or Damaged Air Filter
The other cause of an RV furnace blowing lukewarm air is problems with the air filter. It can become clogged with dirt and dust like a sail switch if it’s not kept clean. Luckily, cleaning or even replacing a faulty air filter is easy, just be sure to choose a filter compatible with your RV’s furnace. An incompatible filter can be another reason for a furnace blowing lukewarm air.
What To Look For When Replacing An RV Furnace
RV furnaces are a game-changer for cold, drizzly days, but things won’t get any warmer if the furnace is blowing cold air instead of hot! If you’ve explored the potential causes of an RV furnace not working and have concluded that it’s time for a new one, there’s a lot to consider!
Size
It may seem obvious, but just like with anything in an RV, it’s wise to measure and check everything will fit into place! RVs can be pretty small, and everything tends to fit snuggly, and the same rules apply to a new RV furnace.
Depending on your rig, it may be possible to relocate the furnace and put the new one in a different spot. This may require some professional help during the installation which will increase the overall spend, but the furnace will be installed safely and securely.
Direct vs. Ducted Furnace
The type of furnace you choose in your camper van is a big decision! The next thing you’ll want to figure out is what type of furnace you want in your RV, direct or ducted. The best way to figure out whether a direct or ducted furnace will work better is to simply take a look at your RV. If your rig is on the smaller side, a direct furnace will work best, whereas larger rigs will suit a ducted furnace better.
This is because direct furnaces blow air from a single large faceplate on the front of the unit. A ducted furnace is what most are used to, with different vents along both the ceiling and roof blowing air throughout the entire rig which is ideal for large RVs.
Propane Usage
If you’re looking to replace your furnace with a new propane-powered one, it’s wise to be aware of propane usage beforehand. Most RV furnaces use around 20,000-50,000 BTUs, depending on the size.
One gallon of propane can supply around 92,000 BTUs, so simply multiply this by the gallons in your propane tank, then divide the figure by the BTUs used by your furnace. This will give you the amount of propane you need to power your furnace.
Carbon Monoxide Detector
While seemingly unrelated to the furnace itself, this is perhaps the most important thing you’ll want to have when choosing a new RV furnace. A working carbon monoxide detector is vital in an RV as carbon monoxide is a byproduct of the combustion process in propane furnaces that heat the air. In small amounts it’s harmless, but in case of a problem with the furnace and large amounts of carbon monoxide are released, you need to know.
Not having a functioning alarm means you’re putting yourself and loved ones at risk of carbon monoxide poisoning which poses a plethora of dangers. With all this in mind, you’ll absolutely be set to make the best decision for you and your rig when replacing your RV furnace.
Closing Thoughts
An RV furnace blowing cold or lukewarm air can be frustrating, especially when camping during the depths of winter! Taking appropriate precautions like keeping the sail switch and air filter clean, and ensuring you have enough propane on board are great ways of preventing future problems with an RV furnace.
Keeping on top of RV maintenance will lead you to happy camping for you and your loved ones in the future. Keep a close eye on your furnace, as it often gets forgotten about, but you’ll soon know something’s wrong when it stops blowing warm air!