RV Furnace has no heat? RV Furnace Troubleshooting Guide

When you are out trying to enjoy a vacation in your RV, the last thing you need is for the heater to stop working. A furnace that won’t function in an RV can turn the whole RV into a portable refrigerator and have you bundling to stay warm. You won’t be able to fully enjoy your vacation if you are shivering and trying to stay warm. This article will help you to identify the problem with your RV furnace and aid you in trying to get it fixed. Ultimately, you may need a professional to work on your RV furnace, but there are steps you can take to try to DIY which will save you time and money and get you warmer, faster!

RV Furnace has no heat? Heres what to do: If your fan on your furnace is running but you have no heat, first check the fuses, breakers, battery voltage, propane tank and regulator, burner pilot light or ignitor, as well as the thermostat to make sure it is sending the heat signal.

How Does An RV Furnace Work?

An RV Furnace works off of the propane tank that fuels other functions on your RV. There will be a thermostat on the inside wall of your RV that has an on button and a dial or gauge for how warm you want to make the temperature inside the RV.

When you raise the temperature gauge, the inducer fan in the furnace will turn on. The fan takes about half a minute to run prior to lighting via a pilot light or ignitor, so the stall from the burner firing up is normal. After another half minute or so after the burners are fired, the blower motor will blow and start to circulate warm air around the RV or trailer. The burner may turn on and off while the fan is on, which is normal if the thermostat measures the set temperature.

Once the camper is up to temperature, the flame will go out and the blower motor will continue blowing for a minute or two to get the last remaining bit of heat out of the heating coils and the fan will shut off.

What Are Some Of The Common Problems With An RV Furnace?

An RV furnace that doesn’t work is a big pain, but most likely there is an easy fix for this problem. However, you have to know how to diagnose where the problem is coming from. There are several tell-tale problems that should allow you to diagnose the cause of the RV furnace not working. With the identification of a certain problem with the furnace, you can usually figure out what is needed to make the furnace start working again.

If you are experiencing a furnace that won’t heat up, but clicks, a fan that is blowing but with no heat coming out, or even a furnace that is silent and seems dead, don’t worry! There may be life still left in your furnace. All you need to do is properly diagnose the problem and follow the steps in repairing or cleaning the furnace so that you can get back to warm and comfortable traveling.

The following list is the most common RV furnace problems and how to fix them so that you can get the heat going again and stay warm.

The Order To Check The Problems Of An RV Furnace

Checking the problems for an RV furnace should follow an order to make sure that you are covering all of your bases from easiest and the most likely problem to the harder, less likely problems.

First of all, check the power supply. There should be twelve volts coming from the battery. Secondly, check the fuse. If they are blown replace them. If they are thrown, turn them back. Checking the propane is next. It might be the regulator or even the tubing. Finally, if all else fails, start to check the furnace and thermostat components such as the thermocouple and heat anticipator. If all of these options are exhausted, call a repair person to come out and make a service call.

Problem #1: Out of Propane

The first thing to check is to make sure you have propane. If you are low or simply out of propane, your furnace in your RV will not light. It will give all of the indications that it will, but at the end of the day, nothing will fire.

This will also happen if you have ran out of propane or not used it for a while. It may take 1-2 cycles of trying to light your furnace to actually start to fire to get the gas pipe full of gas again and air purged.

Always make sure to check to see if you have propane as your first option.

Problem #2: The Burner Will Not Light

You will know that the burner is not lighting on your RV furnace if you look into the device and cannot see the flame or a lack of sound is a sign. The burners typically sound like a jet from the exhaust port so you will know if it is not lit.

Most RV furnaces these days actually don’t have a pilot light, but a direct spark ignition (DSI for short). This is a part that creates a spark in order to light the incoming fuel. You will want to check to see if your DSI is working properly.

A way to test this is to turn on the furnace and look for the sparking or listen for the clicking from the ignition. If you see the sparking of the ignitor and do not see the flame ignite or it ignites for a short period of time, this is a problem. The most common reasons for the furnace not lighting, are the thermocouple position or a bad propane tank regulator.

The Thermocouple

The thermocouple AKA flame sensor is a bi-metal sensor that changes electrical resistance in the presence of heat. The control system recognizes the resistance and makes sure there is a flame keeping the gas valve open. If there is no flame detected, the gas valve will close and the flame will turn off. A faulty thermocouple will turn the flame off every time as it does not sense it even though it may be on.

If this is happening, your thermocouple may not be bad it may just not be sensing correctly. You want the thermocouple to be clean, so take fine-grit sandpaper and sand any soot that may be burned on it causing false readings before turning the furnace on.

If cleaning doesn’t solve the problem, you may have a bad thermocouple.  This is a relatively inexpensive fix. Instead of testing to see if you need a new one, it may just be less trouble to buy and replace. Here is an example of a universal thermocouple that may fit your RV furnace. 

Bad Propane Tank Regulator

The problem with your RV furnace may have nothing to do with the furnace components at all. You may want to check the propane regulator to see if it has gone bad. A bad propane regulator will not send enough fuel to your furnace and it won’t light correctly.

One way to check for a lousy propane regulator in an RV is to light up the gas stove. If the burners have flames that change colors, this is a good indication that the propane regulator is working. The fire should be consistent blue and not switch to yellow or red consistently. It is a great idea to have a backup propane tank regulator and hose if you will be doing a lot of cold weather or off-grid camping since much of the RV functions off of propane gas.

Problem #3: Furnace Only Blows Cold Air

If you can feel the furnace fan turn on, but the air that comes out is cold there are several solutions to get the hot air of the furnace working again. Some problems that you could identify are having a lack of airflow to the furnace or, again, a bad propane tank valve.

Lack Of Airflow

Inside of the RV furnace is an internal switch called the sail switch that registers how much airflow there is. This switch is either open or closed and doesn’t sense a variable amount of airflow. If there is a lack of airflow, the switch won’t allow the furnace to light up. So, the fan will run, but the gas valve will not open and it will not make a clicking sound to ignite.

Sail switches are installed to protect your burners from overheating. If you did not have sufficient airflow, you could overheat your burner and crack your heat exchanger causing permanent damage. These switches are cheap and are can malfunction or go bad.

If this is happening, check to make sure your vents for either return or supply air are not blocked allowing your fan to blow sufficient air.

Clicking Sound But Furnace Doesn’t Ignite

If the ignitor is working in the furnace, the problem does not probably lie in the lack of airflow. Instead, the lack of gas reaching the ignitor could be the issue. You may want to check the propane valve to see if it has gone bad. Also, the thermocouple could also be positioned so that the spark is not reaching the gas coming from the valve.

The factory manual for your furnace will show you the proper gap for your spark to provide the best spark for ignition. Think of a DSI (direct spark ignition) as a big spark plug. Also if the unit was jarred from rough roads, you may need to reposition.

Problem #4: The Fan Does Not Blow Air And There Is No Heat

If there is no fan noise coming from your RV furnace, it may be dead because of a lack of power. However, you won’t have much to go on since there aren’t any components working on the furnace for you to diagnose. You will need to check the battery, check the circuit breaker, and check the fuse for the fan.

There is also a time limit on most furnaces that it will not fire for a predetermined amount of time to avoid short-cycling. This may be a period of 5 minutes, so if you just had it on and now it’s not firing, wait and try it.

Check The Battery

We’ve all done it. The battery on the RV is dead, and now nothing works. However, there may still be enough power to the RV for lighting or other items yet not enough juice for the furnace. If you can check the battery power, see if it has 12 volts coming from it. If it does, the problem is elsewhere.

Check The Circuit Breaker

The next thing you want to check is the circuit breaker. If you tripped the circuit breaker, all you have to do is go to the power panel and reset the circuit.

Check The Fan Fuse

The last thing you may want to check if the battery has juice and the circuit is fine is the fuse for the fan. You should always have replacement fuses for all of the electronics in your RV ready to go as we mention in our article on the top tools to bring in your RV. Simply pop out the blown fuse, which will probably be darker in color or burnt looking, and insert the new fuse. This should fix the problem.

Problem #5: The Fan Will Not Turn On and it was Just Working or it is not Heating to the Proper Degree

If the fan doesn’t turn on, there is possibly a problem with the thermostat. Check the battery is supplying 12 volts first. Then, check to see if you shorted or blew a fuse. If all the electricity components are properly working, you will need to check the thermostat.

What Is The Heat Anticipator?

The thermostat has a precision components in it called a heat anticipator. Basically, the anticipator allows the thermostat to be more or less sensitive. If the temperature of your RV space is around the set degree, it will shut the furnace off.

By changing your anticipator, you change the time in which the furnace will turn back on. If you have your anticipator set to low, it will turn your furnace on and off whenever the temperature of the RV changes by only a small amount would damage the furnace.

How To Check And Adjust The Heat Anticipator On An RV Thermostat?

If you have an analog thermostat, there is manual settings to change. If you have a digital thermostat, you should be able to change within your thermostat’s programming.

On an analog thermostat, the heat anticipator is located under the outer cover and is a metal disk in the thermostat. You have to remove the cover plate of the thermostat to access the heat anticipator. A sliding contact will run over a wire to change the settings.

On the wheel you will see a pointer of some kind that has a little opening in it. This opening reveals the exact setting in amps. It is these amp readings on a silver colored scale that you need to adjust. Read on to find out how.

Adjusting The Heat Anticipator Scale For An RV Thermostat

The average anticipator scale typically ranges from .10 to 1.2 amps. By tuning the heat anticipator to a higher or lower amperage you are setting the thermostat to be more or less sensitive to heat. You will want to consult your manual for your exact settings.

The lower numbers on the amp scale will make it so that the heat will run for a shorter time. This is because it takes less heat in the room for the heat anticipator to tell the furnace to shut off.

Moving the pointer to higher numbers on the scale will make it so that the heat is run for a longer time. This is because it will take more heat in the room for the heat anticipator to tell the furnace to shut off.

Moving the heat anticipator scale should not be messed with unless it is the last resort. Only if this is the last option should you change what the installer set the scale at when the furnace was originally installed.

Conclusion

The design of an RV is not great for cold weather. You are basically in a shell like a refrigerator, so the heat that you build up in the RV goes away quickly. If you are in cold weather, you need to have a heater that works to keep you comfortable and safe during your getaway or vacation.

Remember to always have manuals as well as parts for your equipment before you leave for a trip so that you can do small repairs on vital equipment, like your furnace, while on the road. These replacement parts include fuses, propane tank hookups, and actual parts like the thermocouple.

If you follow these steps to check the symptoms and diagnose your RV furnace, you should be able to make the repair yourself. If you cannot fix the furnace on your own, you will have to make a call to a licensed repair person to come out to your RV and make a service call. Good luck getting warm again!