RV Furnace Won’t Ignite

So, it has happened to all of us, you have turned on the furnace for your RV, you start to hear the blower running, but then it does not end up lighting and the blower ends up turning off.

If this is the first time, do not worry, as this is one of the most common problems people run into with their RV furnace, so we know how to fix it.

So, do not worry about potentially having to get a new furnace as this is something you can fix and troubleshoot easily yourself!

So, if your RV furnace is only blowing cold air, or failing to light, or turns off after just a short amount of time, luckily, we have some simple tricks which have gotten us success in the past.

We will quickly list through some of our top ideas so you know exactly what you need to do to get the best results as quickly as possible.

Firstly, you want to check your propane supply, and once you have done this, check that there is sufficient power supply. Then you check the vents of the RV, and after check the sail switch too.

Then you want to inspect the flame sensor, and after that the limit switch, and finally check the igniter.

If you want more detail on any of these steps, do not worry as we will go into detail on each.

But, before that, let’s give you a brief rundown of how your RV furnace works and why it might not be working!

How Do RV Furnaces Work?

If you want to get the best experience possible when in your RV, then you are going to want to know how the furnace of this vehicle works.

If you do not know this, knowing how to fix it will be a lot more difficult.

There is a high chance that at some point you are going to run into one of the safety features of your RV furnace that is stopping it from being able to work as best as possible.

So, when you are turning on your RV furnace, it is following a safety startup process, so when the thermostat of the device registers that the temperature gets to a point higher than it is supposed to, this will engage the furnace.

The first step that will start up your RV furnace is that the blower motor will turn on, this will then run for somewhere between 15 and 30 seconds until the furnace will attempt to ignite.

This is done to test the exhaust of the blower just in case there are any combustibles that have built up in the system before it can get the signal to ignite.

Then it will start the furnace fan and this airflow will depress a switch known as the sail switch. Once this switch has been depressed it will send a signal to the propane in the system.

This is when you hear a clicking from the igniter, this will be a spark getting applied to the propane which will then burn in the burn chamber of your RV furnace.

Once your RV furnace has been lit, the furnace will slowly begin to heat up.

The temperature should stay within the limit, and it will continue to run until the thermostat of your RV tells it not to when it reaches your set temperature.

If it gets to this excess temperature, the high limit switch will then trigger and this will cut off the fuel supply. However, if this high limit switch does not get triggered, then your RV furnace will just continue to run.

Then there is the regulator which will supply gas to the RV furnace which will then burn inside the combustion chamber.

If you have enough propane gas, your RV furnace will keep running as it heats the air in the exchanger and blows out this hot air until your thermostat recognizes that the heat is too high.

Once this happens your furnace will get the signal to cut off the supply. If the thermostat then asks for more heat the RV furnace will restart the startup process.

Why Is The RV Furnace Not Lighting?

If your RV furnace is not lighting the furnace will notice this and then turn itself off as a safety feature to ensure no propane runs into the furnace without being able to ignite.

This is an important safety feature which is important in keeping you safe.

However, solving what is wrong can be difficult, especially if you have not tried before.

The issue could be the sign of a faulty component, but this does not always mean that you will need an expensive repair.

However, before you call for a repair, there are a few things you can try if you feel like you are handy enough and are willing to use some basic tools.

However, if you are not confident in your abilities, we do not recommend trying anything in this guide as it could be dangerous.

Check Propane

The first step you should try if you are having issues with your RV furnace is also the easiest step and it is also one of the most common issues with the RV furnace.

This is that you could be out of propane, or alternatively, your propane tank valve could be closed. So, if this is happening, your RV furnace will not be getting any propane and this means it will not be able to light.

Because of this, it is worth checking the fuel source levels and making sure that your valve is open to allow the propane to move.

This can be an issue with your propane pressure lock and it is a common issue for RV owners, but it is super easy to fix.

Most RV furnaces have a propane regulator which has safety features that prevent too much gas from leaving the tank at one time.

Because of this, if your tanks are filled, but the furnace still will not start, this is likely the issue that you are facing. So, to fix this, you want to turn off the propane tank and then reopen this slowly.

This will allow your propane to enter the tank at a more controlled pace and solves the problem!

Another potential issue is that if it is a cold night, there is a good chance that your regulator has frozen up and this will prevent the gas flow.

There is a simple temporary fix for this which is just to pour hot water over the regulator, but you also want to dry it off as soon as you are done as this will freeze and then coat your regulator with ice making the problem even worse.

You can also try to turn the stove on to ensure that it lights.

If you have enough propane for the burners, you should be able to have some for the RV furnace.

If your stove is lighting, then you can let it run for a couple of minutes to make sure you are not just burning residual propane from the line.

If other items like the pilot light of the oven and the water heater are still getting propane, then you can be sure that there is still propane in the tank.

If you still do not get propane for the furnace, then you might need to replace your regulator.

Fuse And Battery

Another simple fix that is incredibly easy to miss is checking the fuse and the battery. You should definitely check this before the next steps as it can save you a lot of time.

So, you want to make sure that your RV furnace is getting the power that it needs. Then, you want to check for a blown fuse that could be located in your fuse panel or in your circuit board.

Most of the RV furnaces will run off 12 volts DC power, so you want to ensure that you are checking the fuse itself, and not just a circuit breaker switch.

If this has been blown you will need to replace it, but if the problem continues, you might have an issue with the electrical load because of a broken wire or a component that is malfunctioning!

There is also a chance that you are dealing with low battery voltage if you are using battery power like a lot of RV owners do. This is a problem which is simple to miss if you are using shore power.

For example, if you are at a campsite, sometimes they lose power, but since other parts of the RV function, you have not noticed. To check, just check the outlets and voltage to ensure that you have enough battery.

A low charge battery usually is unable to get the fan to rotate at the speed needed for it to function.

Check Vents

This step is not as common as the others, but it can still stop your RV furnace from working, so you still want to check it now.

While your vent getting clogged is not the most common issue, if your RV furnace is in storage, (see also: 12 Best Storage Solutions For Your RV)it can actually happen quite often.

Because of this, make sure to check your vents at the start of the season as any small opening could make a nest for insects or mice.

You need this exhaust vent to be able to expel the hot air from the combustion chamber, so you need it to flow freely without any obstructions.

This could be stopping your furnace from being able to run, and it could even lead to a fire. So, if you see signs of anything plugin up your vent, you will need to make sure it is cleaned out!

Sail Switch

If you have not heard of it, the sail switch in an RV furnace is a simple switch akin to a light switch, and once it has been engaged it will send a signal to your propane valve to make it open.

So, if your switch is not able to engage, it will not be able to send the signal to the propane valve, and this will stop your RV furnace from being able to ignite.

So, the RV furnace fan will engage the sail switch, so you need to ensure that this is working.

Again, this step is not that complicated to work out, there is simply a thin metal that is inside the body of the blower.

Once your blower is running, the air from the blower forces the switch to close and this then completes the circuit.

However, if your blower is not able to depress, it will not work and then allow the propane valve to open.

If this is not able to open, the propane can not be released and it will not light.

If you want to know if this switch is not working, a simple sign to look out for is when you turn on your RV furnace and hear the blower run, and then the igniter clicks, however, it will turn off without lighting.

This will be because the propane valve never opened, and the main reason for this is that the sail switch never engaged, sending the signal to let it open!

This can be caused by a pretty wide array of different causes, the first one being that the sail switch is simply not working, however, this is not usually the cause.

Instead, one of the more common reasons is that there is lint or fur on the switch that is stopping it from being able to close properly.

So, if you have animals in your RV, this could be a very simple explanation.

This is not helped since RV furnaces do not tend to have an air filter, so if hair and dust is circulating, nothing stops it from going into the RV furnace.

The RV furnace only needs a tiny bit of debris for the whole sail switch to stop working.

However, since this is a common issue, you can remove this switch easily and clean it by hand without that much effort needed.

This could be as simple as a 5 minute task if you have easy enough access to the sail switch.

If you have to remove the furnace, make sure you have removed the supply line connection for the propane.

This is not too difficult, but since you are working with propane, you obviously need to be careful.

Make sure that you have turned off your propane before you start working around it, and you want to ensure that you are comfortable with all the fittings and lines.

This is not just for the sake of confidence, but also so you are sure how to connect it back up safely. Because if you do not, you can create a pretty dangerous situation.

There is another common issue that can cause the sail switch not to work which is a blower that is not performing well enough.

If your blower is not able to create enough of an airflow, you will not be able to engage your switch, this could always indicate a bad blower which is usually a sign of a bad or low battery.

This means that the blower is running, but not fast enough. Fixing this is quite easy though since all you need to do is repair or replace the battery for your blower.

Flame Sensor

As we have inferred a couple of times throughout this guide, your RV furnace has a lot of safety features that are of course useful and important.

However, these can also be the cause of a lot of the reasons why your RV furnace is not lighting, and one of the common ones is the flame sensor.

This will work when your RV furnace lights, there is a sensor inside the combustion chamber, and this detects the flame and sends a current to the control board to say that everything is functioning as it should, however, if it does not sense the flame, then the message is not sent, and the furnace shuts off.

This is actually pretty similar to a sail switch and the issues you can run into with that. This sensor will ensure that the gas flows and the furnace will light and turn the propane.

But, if the sensor does not notice the flame even if there is one, the furnace will shut off. So, if you notice that the furnace is blowing hot air, but all of a sudden shuts off, then this is most likely the issue.

If this is what you are dealing with, then it is not too difficult to fix since the sensor could just be dirty. It can easily get dirty as burning fuel creates moisture and this can make the metal rust.

Also, if your furnace is running rich, like with too much fuel but not enough air, this creates soot which then coats the sensor stopping it from working as well. So, all you need to do is give it a good clean!

Limit Switch

After your sail switch has engaged, it is going to send power to your gas valve which then sends propane to your furnace. The gas valve is occasionally a problem, but this is not very common.

So, if the sail switch is working and the gas valve is powered, it will attempt to light and the chamber will heat.

What checks the range of the heat is your limit switch, and if this is not working, the blower will run, you will get heat, but then it will turn off after blowing some cool air.

So, if you think your limit switch is faulty, you will not be able to hear the furnace clicking to ignite and it will not work.

There is also a chance that it will not work because of a lack of air flow due to a blocked duct.

To stop this from happening, you want to make sure the air ducts are not obstructed and are able to flow freely.

The best way to get your limit switch to work again is to replace it, this is usually due to a bad connection, luckily this task is not too difficult.

Igniter Or Electrode

The final main reason that your RV furnace is not igniting is because of an issue with your igniter/electrode.

To check if this is the issue, you will want to inspect if this part of your RV furnace is working.

The sail switch, if working, sends a signal to your limit switch to light, and then you will hear the click of the propane being lit.

So, if the sail switch, and limit switch are both working, then the issue is with the igniter. This does not fail as often, however it is still a possibility.

When you are checking for issues with this part of your RV furnace, you want to see if there is any corrosion or if the metal arm is broken.

If there is a break in one of the two pieces of metal that is used to make the spark, it will not be able to do this, and it is broken.

And if the gap has gotten too wide or too narrow, this is also not possible.

You ideally want the gap to be 1⁄8 of an inch, so if you want to measure this easily, use a drill bit of the same size to measure this. You will either want to try carefully adjusting the distance or replacing the part.

Summary

It is worth noting here that these are not the only things that can cause your furnace not to work, however, they are the most common issues which are easy to fix.

For example, if your fan is blowing, but the furnace still does not light and then turns off after your light, then a lot of the previously listed problems are usually to blame.

So, if you are comfortable working with appliances like these, and you are able to diagnose and repair these problems yourself, you can save a lot of time and money.

However, if any of these steps or ideas make you uncomfortable and you are unsure if you will be able to pull them off properly, then visiting a repair shop or contacting an RV tech will save you a lot of time, and potentially, from damaging your RV.

For example, if it is cold weather, but you are uncomfortable, you will want to get your furnace fixed as soon as possible to stop your pipes from freezing, and working under stress like this can cause issues, so getting a tech to help is important.

Another issue that we have not been able to address in this guide is that your furnace might have a bad control board, which is the brains of your furnace.

This is a lot more complicated, and a lot more expensive to fix, so if you are not a professional, then getting the help of a professional is definitely recommended.

Other repairs not mentioned here that are easier for a tech include a bad gas valve, or a new thermostat as well.

If you know how your RV and components like your furnace work, this can give you a lot more confidence during your travels, especially if you have run into awkward situations and problems like this before.

You should keep in mind that a lot of replacement parts for the furnace are pretty easy to access and most are affordable, so this is not something to stress about.

Make sure to stay on top of maintenance for your RV, to ensure you fix issues as soon as possible, as this makes them cheaper and easier to fix!