How To Troubleshoot RV Furnace That Wont Ignite

RV vacations don’t have to be limited to just the warm summer months. In fact, there are some people who enjoy RV travel year-round, and others who double up their RV as a mobile hunting shack in the fall.

In situations like this, a heater or furnace plays an essential role in keeping you warm through the night and maybe even keeping you comfortable during the day.

Yet, what happens when the furnace doesn’t work properly? What do you do if your RV furnace won’t ignite?

With a little patience, and mechanical know-how, you might be able to diagnose the problem, and maybe even fix it yourself.

If nothing else, having a better working knowledge of what’s going on, will reduce the number of man-hours that a repair shop has to put into it. 

In this article, we will look at some of the more common problems in RV furnaces, how to diagnose them, and whether or not you can fix it yourself.

Reasons Why Your Furnace is Not Igniting

There area a few different things that can prevent an RV furnace from igniting properly or cause it to work intermittently. Some Common Causes Of A Propane Furnace Failure Include:

  1. Problems with the propane tank
  2. Problems with the propane line
  3. A burned out thermocouple and pilot light
  4. Problems with the thermostat
  5. Problems with airflow
  6. Simple electrical issues

Why is my furnace not working in my camper?

The answer to this question can vary a little depending on the type of furnace you have. If you have a propane furnace or wall heater, the first thing to check is the propane tank which might be the main reason of ignition failure on a RV furnace . Obviously, the valve needs to be turned on for it to deliver any of the hydrocarbon gas to the heater/furnace.

Yet it’s also worth bearing in mind that in cold temperatures, propane can contract a little bit, which can reduce the pressure inside the tank.

It’s possible that the tank might be low enough, and the outside temperature is cold enough that the tank essentially froze up.

If the inside of your RV is relatively warm, you can bring the tank in to warm it up. This might be a real pain in the neck if it’s a large tank or it has heavy-duty fittings holding it in place. 

Once the tank warms up, you can install it back outside again. If the furnace maintains a continuous draw, you just might be able to make it through the night.

If you have a spare tank available, you should try switching over to it and see if that rectifies the problem.

At the same time, you shouldn’t discount the possibility of a leak in one of the propane lines. Sometimes in cold weather, a fitting can come loose, or an old gas line can fray or crack.

When this happens the propane simply can’t reach the furnace to give it a chance to fire.

How To fix a RV furnace that won't ignite

1: Diagnosing A Problem With The Propane Tank Gas Lines

Diagnosing a failure with your propane tank or gas lines starts with assessing if any gas is available.

You can do this by turning on the internal propane range, setting a two-way refrigerator to propane, or igniting any other appliance that runs off the same gas line.

If it works, then you can rest assured that it’s not the propane tank or the lines. If you find no evidence of gas being available in the system, you should inspect the system starting with the external tank.

2: Addressing A Problem With A Propane Tank Or Gas Lines

It’s not unheard of for a propane coupler to come loose in cold weather as the metal contracts. Take a moment to check them all to make sure there are sufficiently tight.

If there was a leak in an internal line running through the RV, you would notice the telltale smell of rotten eggs.

If the leak is outside on the mainline, it might be harder to detect with just your sense of smell. If possible, run a bare hand along with the line feeling for any cracks or damaged areas.

Make sure to check where the propane line enters the camper body. Sometimes gaskets here can wear on a hose causing a minor leak.

In a pinch, you might be able to wrap a small leak with a copious amount of duct tape. If it works, it might get you through the night, but it’s not going to be a permanent fix.

3: Minor Electrical Problems Can Cause causes ignition failure

The igniter on most RV propane furnaces needs at least 10.5 Volts to fire properly. If one or two of your onboard batteries has run desperately low or has been compromised, there might not be sufficient spark to ignite the system or operate the thermostat.

Sometimes it’s simply a matter of a circuit breaker tripping. So, check the panel to make sure all the breakers for the furnace and thermostat are in the “On” position.

How To Fix An Electrical Failure In The Propane System

If possible, try switching over to a backup battery that can produce more than 10 Volts.

In a moment of desperation, you might be able to use the 12 Volt battery from the motorhome or tow vehicle, but this is a “Last Ditch” sort of thing. The last thing you want is to be stuck in the woods with a dead vehicle battery as well.

4: A Wiring Problem Could Prevent Electricity From Igniting The Furnace

If the onboard batteries show that they are delivering sufficient power to the system, you should check to see if the problem is related to damaged or loose wire. This requires a meticulous approach while following wires.

It might help to start at the furnace itself. Double check all of it’s connections and wires. Sometimes the vibration of driving can rattle a wire loose, or cause a connector to fall out.

It’s also possible for a wire to become overloaded, and short out or the protective coating is damaged. 

5: Determining If It’s An Electrical Problem

The igniter on most RV propane furnaces needs at least 10.5 Volts to fire properly. If one or two of your onboard batteries has run desperately low or has been compromised, there might not be sufficient spark to ignite the system or operate the thermostat.

Sometimes it’s simply a matter of a circuit breaker tripping. So, check the panel to make sure all the breakers for the furnace and thermostat are in the “On” position.

6: Dealing With A Low Or Dead Onboard Battery

A quick check with a multimeter will tell you how many volts are being delivered to the furnace. If it’s less at 10 Volts, then the problem is likely one of your onboard batteries.

Without sufficient power isn’t being delivered to the thermostat or the furnace it won’t be able to ignite, and the fan might run slowly or not at all.

If possible, try switching over to a backup battery that can produce more than 10 Volts. In a moment of desperation, you might be able to use the 12 Volt battery from the motorhome or tow vehicle, but this is a “Last Ditch” sort of thing. The last thing you want is to be stuck in the woods with a dead vehicle battery as well.

7: Battery Corrosion Can Interrupt Service

Take a close look at the battery terminals and the connectors. As time goes on electrolytic corrosion can cause a white, gray, or even greenish material to buildup on a terminal.

Left unchecked it can prevent power from being delivered to the furnace system. Sometimes a simple cleaning is all that’s needed to reestablish an effective connection.

How To Clean Corroded Battery Terminals

  • Step One: Create a slurry mixture of baking soda and water.
  • Step Two: Carefully disconnected the connections and wires from the corroded terminal.
  • Step Three: Apply the baking soda slurry to an old toothbrush and carefully scrub away the corroded material.
  • Step Four: Use a clean paper towel to thoroughly wipe off the baking soda.
  • Step Five: Reconnect the wires to the terminal, and check to make sure power is being delivered to the RV’s internal lights, the thermostat and the furnace.

8: A Wiring Problem Could Prevent Electricity From Igniting The Furnace

If the onboard batteries show that they are delivering sufficient power to the system, you should check to see if the problem is related to damaged or loose wire. This requires a meticulous approach while following wires.

It might help to start at the furnace itself. Double check all of it’s connections and wires. Sometimes the vibration of driving can rattle a wire loose, or cause a connector to fall out.

It’s also possible for a wire to become overloaded, and short out or the protective coating is damaged. 

9: A Damaged Wire Cause A Furnace Not To Ignite

If this doesn’t improve the situation, you should then check for any loose wires or connections between the battery and the furnace ignition system.

Sometimes something as simple as corrosion on a battery terminal can prevent the necessary power from being delivered effectively.

If a wire or connection is loose, you will need to tighten it or perhaps clip, strip, and secure it with a wire nut. A damaged wire might need to be patched, spliced or maybe even replaced altogether.

If the terminals on the battery are corroded, cleaning them with a mix of water and baking soda, and scrubbing with an old toothbrush might improve the connection enough to deliver the necessary power.

How To Replace A Damaged Section Of Wire

  • Step 1: Use a wire cutter to snip out the damaged section.
  • Step 2: Carefully strip back an inch of protective coating on the two exposed sections of wire.
  • Step 3: Take a new section of wire that is a similar or thicker gauge and strip the protective coating by an inch on each end.
  • Step 4: Braid the exposed ends of wire together. You can then solder them and wrap with electrical tape or twist them securely in a small wire nut.

10: A Thermostat Problem Could Cause A Failure In The Propane System

The thermostat is essentially the “Brain” of the heating and cooling system. While they are meant to last for a long time, it’s not unheard of for one to burn out or have a component fail.

In a lot of these cases the sensor inside it dies, and you will need to reaplce the entire unit.

However, there are times when something like a loose wire or a dead battery can cause the thermostat to fail.

When this happens the message to ignite the furnace isn’t sent and the safety systems in the furnace don’t deliver any gas.

11: Check And Tighten Any Loose Wires On The Thermostat

If you have a digital display panel on your thermostat and it is blinking, or giving wildly inaccurate numbers, it might be due a loose wire.

To check this, you need to carefully remove it from the wall. Check all the connections. Some are held on by tiny screws that can come loose and just need to be tightened again.

12: Checking And Replacing Internal Thermostat Batteries

In some RV’s the thermostat isn’t directly connected to the onboard 12-Volt batteries. These units often run on AA or AAA batteries.

In many of these cases you will see the display screen blinking, refusing to acknowledge the press of a button, or even giving you a blank screen.

In a case like this, you might need to simply replace the batteries. While you are at it, check for corrosion on the connections.

Then turn the thermostat on and give it a minute or two to reset it’s internal program. If it is indeed a simple low battery problem the thermostat should act normally, and the furnace should fire again.

rv furnace blower comes on but won't ignite: What to do 

There are also times when the RV furnace might ignite, but the blower won’t deliver the hot air or delivers a weak stream of air. There are a few things that this could be such as:

  1. A pilot light problem
  2. A failed thermocouple
  3. A blower fan failure
  4. A ventilation issue

1: Dealing With A Pilot Light Problem to fix 

Pilot light problems are sometimes related to failed safety sensors or airflow issues which causes the furnace blower will come on but not to ignite. The two place to check first are the thermocouple and the sail switch. A sail switch is essentially an on/off switch, that detects if there’s not enough airflow. In a situation like this, it will stop the furnace from igniting but blower will begins to blow.

However, the fan will still likely run. The sail switch is more likely to fail or burnout if there isn’t sufficient return airflow or insufficient venting. They also are prone to sticking from time to time.

If the fan is running but there is little heat, chances are the sail switch is having a problem. To troubleshoot it here are few things you can do.

  • check to make sure your battery is sending 12 Volts to the furnace unit.
  • You should also check the breaker box to see if the furnace breaker or fuse has blown.
  • Next, double-check the vents for any signs of dust or soot buildup. This includes the RV exhaust vent. If you are seeing soot buildup, then chances are the furnace is developing improper or inefficient combustion.

2: Identifying A Sail Switch Problem

A sail switch is essentially an on/off switch, that detects if there’s not enough airflow. If something has clogged the air intake or exhaust vent, it might stay in the off mode or off position.

When this happens the fan might turn on and try to blow or blow poorly. It might also tell the rest of the safety system to prevent the furnace from igniting.

If you notice cobwebs or other debris in the air intake or the exhaust vent, try clearing them. Next, double-check the vents for any signs of dust or soot buildup.

This includes the RV exhaust vent. If you are seeing soot buildup, then chances are the furnace is developing improper or inefficient combustion.

After any debris has been cleared, you should reset the system by turning the furnace or the thermostat off. Give them a solid minute, then turn the power back on.

At that point the system should try to run normally. If the fan is running but the furnace still isn’t igniting chances are something technical has gone wrong with the sail switch and you need to replace it.

To troubleshoot it, you first need to check to make sure your battery is sending 12 Volts to the furnace unit. You should also check the breaker box to see if the furnace breaker or fuse has blown.

3: A Compromised Thermocouple Can Prevent Pilot Light Ignition

A thermocouple is a special safety component in most gas furnaces. It is essentially a sensor that measures the temperature at the furnace measure temperature.

It consists of two wires made from different metals that are carefully joined together to create a junction.

The thermocouple itself puts out a millivolt signal. If the resistance changes, it measures the voltage. Any change in resistance is then detected by the furnace’s control system.

It essentially ensures that there is a flame at the pilot light before it activates the main gas valve.

When a thermocouple burns out or breaks down, the furnace won’t release gas and the pilot light goes out. Sometimes it’s also a matter of spider webs and dust that needs to be cleared away before the thermocouple works correctly.

It’s hard to tell if a thermocouple is burned out just by looking at it. Sometimes it will cause a rotten egg smell when you first turn the heat on.

If everything around the thermocouple looks clean, and all the other electrical components are properly connected, you should check the thermocouple with a multi-meter.

If it doesn’t show any power being delivered to the thermocouple, it likely needs to be replaced.

Fortunately, a new thermocouple is relatively cheap and easy to replace. Hardware stores and RV dealerships will likely have a replacement for your model furnace.

If there isn’t one nearby you might need to make it through the night with a portable sunflower heater, or run the motorhome’s engine with the heat vents on.

4: A Damaged Or Failing Blower Fan

This could be two different things. If you are getting a little heat, but the fan has weak output, it might be the fan motor going out.

This is more likely to occur with an older RV. It’s often related to the internal bearings or bushings wearing out. However, it could also be a wiring issue.

Double-check to make sure there aren’t any cobwebs, dust or other debris impeding the fan blades. While you are at it, feel the motor housing. A fan with bad bearings or bushings will give off a lot of heat.

Most blower fans have soldered wire connection. If one of them has pulled loose, the circuit won’t complete and the fan won’t fire. Sometimes a connection comes loose, causing low power or intermittent power.

If you find a broken or loose connection, try soldering it back in place. Then reset the system and see if the blower will run like normal.

Dealing With A Dead Blower Fan

If the blower fan itself is dead, or it’s making a terrible noise, you will likely need to replace it. This calls for finding a similar fan that will fit into the housing.

Sometimes this is as easy as walking into a hardware store with the burned out fan. Other times you may need to special order a new blower fan, which could take more than a day or two to ship to you.

Replacing A Dead Or Damaged Blower Fan

If you are particularly handy, with the proper tools and time, you might be able to replace the blower fan yourself. If you aren’t comfortable with this, you might want to seek professional help for the removal and install.

  1. Step One: Turn off the electric circuit breaker.
  2. Step Two: Loosen all the fasteners holding the blower fan in place.
  3. Step Three: Disconnect the wires from the back of the blower fan. This might take a heat gun or a soldering iron. With some you might only need to loosen some small screws.
  4. Step Four: Connect the old wires to the new blower fan’s ports. If necessary, you might need to solder them in place to provide a secure connection.
  5. Step Five: Insert the blower fan back into the housing and retighten all the fasteners.

At that point you should turn on the breaker and try to turn the system back on. The furnace will need time to ignite and develop hot air. The new blower fan should then deliver hot air like normal.

Tips For Staying Warm In A Furnace Emergency

RV furnace problems tend to happen at the worst possible times. It’s always a good idea to double-check your RV’s heating system before going on a trip where you think you’ll need to use it.

Yet even with all due diligence and proper maintenance, there might still be times when your furnace goes out unexpectedly.

If it’s particularly cold inside the RV, your first step might be to set up emergency heat. Especially, if you can’t get the RV to a safer location.

If your hands get too cold, you might lose the dexterity you need to identify and fix the furnace problem.

If you don’t have the parts to repair the problem, and it’s too difficult to pick up and move for the night, there are a few things you can do to keep warm.

It’s always a good idea to keep a small sunflower heater and a pair of one-pound propane canisters in an emergency locker for some quick heat.

If it’s not desperately cold, you can try lighting some candles just to keep the ambient temperature warm.

If you have fire-rated bricks on hand, you might be able to wrap them in tinfoil and place them in an outdoor campfire for half an hour.

They will gradually absorb the heat. You can then bring them into the RV and place them on the stove to radiate that heat. This can also give you a way to warm up your hands while you work to diagnose the furnace problem.

In Conclusion

Taking a systematic approach to diagnosing your RV furnace problems plays a critical role in affecting a speedy repair.

In some of these cases you might be able to repair it yourself. Though there are some times when the problem is too technical for a do-it-yourself to tackle.

If professional intervention is necessary, and you can’t immediately get to a repair shop, you may need to improvise for a night or two to stay warm.

1 thought on “How To Troubleshoot RV Furnace That Wont Ignite”

  1. Thank you for writing this. From now on maybe I can fix furnace by myself without the assistance of an electrician.

    Reply

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