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RV Furnace Troubleshooting: 2023 Detailed Guide With Wiring Diagram

If you are looking for RV furnace troubleshooting guide you are in the right place! We will help you in dealing with different issues related to ignitors, air vents, RV furnace fan, or thermostats.

So, continue reading to learn about the methods to detect problems via error codes, the 7 often problems, and their solution. Also, scroll down and you will find a diagram that will help you understand the RV furnace.

Let’s get started!

Working Mechanism of an RV Furnace

The main principle of working in a furnace is burning fuel (usually propane or natural gas) to produce heat. Several components make up the whole forced-hot-air system. The components are:

RV Furnace Troubleshooting. Working Mechanism of an RV Furnace
  • A thermostat
  • An RV furnace control board
  • A relay, a sail switch
  • A blower motor
  • A high-level switch
  • Ductwork

Here is a detailed overview of its working!

  • First, you must set the thermostat to a higher temperature than the indoors.
  • Once this is done, the furnace works by activating the RV furnace blower motor.
  • Airflow starts to circulate into the RV. After about 15 seconds the control board detects (through the flame-sensing rods) and ignites the propane.
  • The burning propane produces warm air through the process of combustion which is distributed through the RV ductwork to the different parts of the RV.
Note: The whole system relies on the electronics which usually consist of a battery that supplies a 12V DC charge and the fans.

Understanding the RV Furnace Diagnostic Codes

Diagnostic codes communicate the malfunction or problem occurring in the system. They signify the problem with a flashing LED on the furnace panel. The number of times the light flashes needed to be counted accurately to record a code. It is more like a Morse Code!

Understanding the RV Furnace Diagnostic Codes

The interpretation of the code can be found in the owner’s manual or on the sticker present on the furnace. Listed below are the very common codes:

  • Code 31
  • Code 32
  • Code 33
  • Code 34

The interpretations of the codes are mentioned below. Let’s learn more about them!

What does Code 31 mean?

The following code identifies a problem with the airflow. Common reasons for the problem are a dirty filter, a faulty RV furnace blower motor, or even a blocked intake of air.

What does Code 32 mean?

If you encounter this code then it means that the ignition system in the furnace is problematic. Check the electrode for any dirt deposits, a weak spark, or a fault with the gas valve.

What does Code 33 mean?

This flashing code communicates that a safety mechanism has activated shutting down the furnace which is usually due to a malfunction in the heat exchanger. This happens when the limit or flame rollout switch trips.

What does Code 34 mean?

A problem in the furnace’s ignition sequence generates this error code. Check if you notice any blockage on the burner opening, a fault in the gas supply outlet, or any issue with the ignition control board.

RV Furnaces: 7 Common Problems and Their Fixes!

After some time you may likely face certain technical problems in the RV furnace. Here are some common problems that you may encounter and their solutions. Let’s have a look!

1. RV Furnace Isn’t Functioning Properly

You may turn the furnace on and it does not work. This happens due to several reasons some of which are failure to channel power from the 12V battery. Also, coordination between the thermostat and furnace results in such an issue.

RV Furnace Isn't Functioning Properly

Ensure that the power source is properly plugged in and batteries are charged. Then follow the steps given below:

  • Take out the DC fuse from the panel and check for physical problems. You can use a multimeter to check it.
  • If the fuse is fine then there is likely a problem with the connecting wires to the furnace. Check them with a multimeter.
  • In case the power flow through the wire is also fine there can be a problem of communication between thermostat and furnace.
  • Check the thermostat control panel mounted on the wall. You can take it out and inspect the connections and wiring.
  • Digital thermostats can be checked via their digital panel. If the display doesn’t turn on then it has broken down and needs replacement.

2. The Fan Works Perfectly but Heat is Not Produced

You notice that the furnace blower fan is on but the heat does not come out. Instead, you notice cold air coming out! This happens when there is a problem with the ignition, sail switch, the circuit board is causing problems, or the fuel is not igniting.

The Fan Works Perfectly but Heat is Not Produced

There may be multiple reasons for this specific scenario. Below is a list of possible problems that can cause the failure of heat production even when the fan is working. Let’s have a look!

1. Examining the fuel supply:

Here is how you can check the fuel supply for any problem. Let’s learn about it!

Examining the fuel supply
  • Check if the fuel lines are supplying the fuel properly. Check the pump with a voltmeter/multimeter if the fuel pump is working.
  • Check if the propane gas is turned on and the pressure is stable.
  • Turn on a stove or any other gas appliance to check the pressure.
Note: You need a pressure gauge!

2. Double-Checking the Battery Voltage:

Having doubts about the battery voltage capacity? Here is what you need to do!

  • The blower fan can run on a low battery but the combustion chamber needs high voltage to ignite the propane.
  • The problem can be in the sail switch. If you notice 10.5 volts which is not sufficient for the furnace to operate.
  • Recharge the battery to maintain the voltage.
  • If the battery is worn out then change it.
Pro Tip: Installing an RV battery monitor can display the statistics of the battery. You can check the voltage on it and recharge it if needed.

3. Checking the Airflow:

Do you hear any sounds or suspect a blockage? Follow the steps below to check!

Checking the Airflow
  • There is most likely a blockage in the air intake.
  • Leaves, pests, nests, debris, or other type of insects can inhibit the space.
  • Maintain the air intake by regularly checking and cleaning it.

4. Resolving Issues with the Sail Switch:

Follow the steps to resolve the issues with the sail switch. Let’s get started!

  • Corrosion or loose fitting is one major reason for this problem. Clean it or tighten the fitting.
  • Check the gas valve if it is working properly.
  • Inspect the propane tank and the pressure it is generating. Use a pressure gauge to confirm this!
Pro Tip: If you are unsure of how to fix it then seek professional help.

5. Checking the Ignitor:

If the propane is not igniting properly then the steps below can solve the problem. Let’s get started!

Checking the Ignitor
  • Inspect the furnace ignitor as it produces a noticeable clicking sound.
  • If a sound is not heard then there is a problem.
  • Check the ignition circuit next. First, take a look at the sail switch if it is not tripped.
  • Once confirmed, check the high-voltage ignitor circuit now.
  • Inspect the relay for the ignitor at the circuit board for a consistent flow of power.
  • If the flow of power is okay and the ignitor is not firing then the final analysis is that the coil is bad. So you need to replace the coil.

3. The Furnace Stops/Starts from Time to Time

Two major faults cause this problem! Firstly, a damaged thermostat. Secondly, a problem with the environment surrounding as the temperature of the air might be higher than expected. Warm air may hit it directly. It will record that airflow as the room temperature and shut down.

The Furnace Stops/Starts from Time to Time

Listed below are instructions to fix the furnace issues:

  • If the thermostat is causing problems or you notice a fault then immediately change it.
  • Duct registers (used for directing the airflow) can be a cause of the problem! Change its location a little further so that the thermostat does not turn off prematurely.
  • A thermostat with a leaky seal will detect inaccurate temperatures.
  • Avoid placing the thermostat in rooms that are warmer for example, near the kitchen, a fireplace, or a refrigerator.
Pro-Tip: Install a ceiling fan in your RV to evenly distribute the warm air and avoid this problem.

4. The Thermostat Temperature Setting is Right but the Furnace Stays On!

Sometimes the desired temperature is achieved but the furnace keeps working and does not shut off. In such a situation, more heat will circulate in the RV and the situation can get out of hand due to high temperature.

The Thermostat Temperature Setting is Right but the Furnace Stays On!

First, using a multimeter you need to check the voltage from the thermostat to the delay switch. Then follow these guidelines:

  • If a voltage reading can be recorded on the device then the thermostat has failed. The thermostat responsible for controlling the furnace’s functions is not working properly and needs to be replaced.
  • Next, you need to check the fuse box. It is the black box underneath the cabinet or stairwell.
  • Open it and locate the RV furnace fuse. It will be labeled. If not, check the owner manual.
  • If you notice a blown fuse then immediately replace it.
  • In case there is a short circuit, use the multimeter to locate the fault.
  • Change the wires causing the issues and also the fuses.
Pro tip: Consult the user manual/owner guide for a wiring layout or seek professional help if you are still confused.

5. The Furnace Doesn’t Work via Battery

The 12-volt battery is the main source of power for the furnace. But, if the battery fails to supply enough charge but the furnace functions perfectly with a shore power/generator. Then the common reasons are that the battery is not charging, is faulty, or the terminals are corroded.

The Furnace Doesn't Work via Battery

Use a multimeter to check if the battery output is 12 volts. Fully charging the battery can power the furnace properly. Then follow these steps:

  • If the battery cannot store enough charge and it keeps dropping then there is a fault in the battery.
  • Inspect the battery at least once a month for any signs of corrosion.
  • If the posts have corrosion then disconnect the cables. But, remove the -ve terminal first.
  • Now clean the posts and also the connectors.
  • Make use of a terminal cleaner for better results. You can also make your own. Here is the recipe: 1/4 cup baking soda and 1-1-1/2 cup water.
  • Spray the above-mentioned mix on the post and the corrosion will quickly break down. Caution: Disconnect the battery terminals completely before doing this. And wear safety gloves.
  • You need to apply it for a few minutes.
  • Now rinse the posts with plain water.
Pro tip: Using a lithium-ion house battery will prevent the risk of RV battery failure.
Caution: Never discharge a battery (lead-acid type) with a voltage output below 12 volts (common voltage capacity for RV furnace battery). This causes damage to the battery.

6. Extremely Weak Air Flow via Duct/Exhaust Vent

This problem is due to blockages, holes in the exhaust vent/duct, or improper/loose fitting. Air-escaping leakages will not distribute well in the RV.

Extremely Weak Air Flow via Duct/Exhaust Vent
  • First, check the air intake for any debris collection.
  • If that is clear then check the ends of the duct to see if they are tightly fitted.
  • Now check the ducts all the way to identify if there are any holes in it. The Fix: If you find any holes then use an aluminum tape to mend them.
Important note: Some RV furnaces will not start working if the external furnace cover panel is absent. Make sure the cover is on the furnace perfectly.

7. Loud Noises Coming from the Fan

Check the blades of the furnace fan if they are hitting the housing. Another reason could be debris, lint, or any other collection of unwanted stuff. Check the fan motor if it has a loose or damaged bearing.

Loud Noises Coming from the Fan

Start by checking the housing for any debris. Clean it properly. Then, follow the steps mentioned below to fix the loud noise issue:

  • Grease the motor shaft beside the motor. Spin the furnace fan by hand and notice if there is any noise. If there is no noise then the issue is fixed.
  • If the problem persists then check the fan housing for a loose screw.
  • Tightening the screw will fix the problem.
  • Another reason is the bearing that is either damaged or worn out.
  • You need to change the fan motor if the bearing is bad.
Pro tip: Purchase an RV vacuum to prevent dirt, dust, or lint accumulation in the rig.
Caution: Disconnect any power source from the furnace before doing this!

RV Furnace Blower, Heat Exchanger, and Other Essential Parts

Knowing the functionality and parts that make up the whole RV furnace system is essential knowledge. Understanding the different parts allows you to identify them while troubleshooting errors. Listed below are some important parts of the RV furnace. Let’s learn more about each part!

RV Furnace Blower, Heat Exchanger, and Other Essential Parts
  • Air Return: Takes in the air to circulate through the heat exchanger and then out of the ducts.
  • Blower Motor: Motors are used to operate fans for the circulation of air through the furnace.
  • On/Off Switch & Circuit Breaker: They control the power to the blower motor. Circuit breaker trips in case of any issue for example short circuit.
  • Combustion Air Intake: Located on the external end of the RV it pumps air into the combustion chamber.
  • Combustion Chamber: Propane and oxygen combust here to generate heat for the furnace.
  • DSI: DSI (Direct Spark Ignition) is an electronic ignitor that generates a spark to burn the gas-air mixture.
  • Ducts: They circulate heated air coming from the furnace into the interior of the RV.
  • Exhaust: Throws out poisonous gases produced during the combustion process via the exhaust vent.
  • Fan Speed Controller: Controls the speed of the fan and adjustment of BTU output.
  • Heat Exchanger: Warms the air in the ducts by taking heat from the combustion chamber via conduction.
  • Gas Valve: Controlled by the circuit board, this valve is electronically controlled to release gas into the combustion chamber.
  • High Limit Switch: Regulates the heat and ensures that the heat exchanger does not get damaged. It cuts the power if temperature readings are above the limit.
  • Igniter: Produces a spark to initiate the burning of propane. In a DSI furnace, it is present instead of a pilot light. It is also a sensor to detect successful ignition.
  • Pilot Light: Ignites a small flame constantly lighting any propane when the valve is open. Note: Ansebt in a DSI furnace.
  • Sail Switch: The sail switch stops the air from the blower. When the blower goes fast, it moves it away, so power can go to the ignition switch.
  • Thermostat: The thermostat checks how hot it is inside the RV. If it's not hot enough, it turns on the furnace to make it warmer.
  • Time Delay Relay: It waits for a short time before starting the furnace cycle. [/su_note]

Standard Diagram of RV Furnace Wiring System

The furnace diagram will help you locate all the important components and their connections. Here is a diagram to help you out!

Standard Diagram of RV Furnace Wiring System


What are the most common RV furnace problems?

Some of the most common RV furnaces problems can be identified with the furnace shutting down within 30 seconds, the furnace does not turn on when the thermostat is adjusted, the furnace blowing cold air, the fan spinning but propane does not burn, and so on.

How do you troubleshoot a furnace problem?

The best way to troubleshoot a furnace problem is by identifying the problem either by understanding the code or by physically inspecting the furnace system. Certain indications will give you hints about the source of the problem such as no ignition, less airflow, etc.

Why will my RV furnace not ignite?

The RV furnace ignitor does not work due to some common problems with the onboard batteries. They must have worn out or got damaged for some reason. Also, the circuit breaker can trip as a safety measure so which also causes this problem.

How does RV furnace work?

RV furnace working depends on the type of furnace for example some RV furnaces operate by blowing hot air from the faceplate of the device. A ducted furnace will circulate air via ducts that channel through the ceiling or flooring.

Is RV furnace AC or DC?

The RV furnace system runs with the help of a 12V DC battery. Although, it can also run via a shore power source or a generator.


Troubleshooting the furnace consists of identifying the root of the problem and resolving it. It ensures that any further damage or malfunction does not occur in the furnace.

Common problems like cold air flow can be resolved by checking the ignitor or ignition board. Damaged ducts can be another problem that can be easily fixed using duct tape.

But if you are unsure of the methods then getting help from a professional is the best approach. Which error code did you encounter and how did you resolve the problem? Let us know in the comments section if the problem was fixed!

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