Atwood Furnace Ignition Lockout Fault [9 Easy Fixes]

Ignition lockout fault on furnaces is one of the most common errors that occur. There are many possible reasons behind an Atwood furnace ignition lockout fault.

atwood furnace ignition lockout fault

Here’s what causes furnace ignition lockout more commonly – low gas pressure, blocked exhaust, and loose combustion air wheel.

Also, a defective circuit board, bad heat exchanger, low voltage, blocked burner head or orifice, broken thermostat, and faulty flame sensor are in the same line as a culprit.

Keep reading our guide on how to fix the ignition lockout on the furnace and fix your issue ASAP.

Table Of Contents

Atwood Furnace Ignition Lockout Fault [9 Easy Fixes]

In this section, we will take a look at troubleshooting the Atwood RV furnace ignition lockout fault. Explore the causes and their simple solutions in more depth.

Note: You can also read how to fix the Sta-Rite pool heater ignition lockout problem.

1. Low Gas Pressure

The pressure reading of your furnace should be 11″ W.C. (water column) or 27 bar using a U-Tube water manometer, with the furnace and all gas appliances turned on.

Ignition lockout, sooting or premature combustion and heating chamber failure are common side effects of low gas pressure. 


You need to attach a manometer to the gas valve. You need to remove the 1/8″  MPT plug that is placed on the valve’s outlet part. You need a ⅛” brass barb to insert into the empty space for the MPT plug that you removed.

Threading sealant is recommended to guarantee that the barb tap is secure and that no gas escapes from the sides, falsifying the measurement.

The burner can be turned on once the digital manometer is attached to the gas valve. The gas pressure can be altered by rotating the gas pressure adjustment screw (Clockwise rotational motion -> increase pressure).

2. Blocked Exhaust

Your Atwood furnace needs an exhaust to let out the combusted air and heat. If dirt and debris are blocking the heater exhaust, all that heat is trapped inside.

This causes the heater to overheat and shut off due to safety. Your burner will be turned off as well causing ignition failure.


Here’s how you clean out your heater vent.

  • Find the vent pipe for your furnace. Remove the vent cap with the screwdriver while wearing gloves, eye protection, and any other dust protection. 
  • You should be able to see inside the vent once it’s opened. Use a wire or plastic hook to reach any debris that has become lodged. 
  • Scrub the inside to remove any dust and debris, then vacuum as much as you can with the handheld vacuum. Replace the cap after wiping it clean with a rag or soft cloth. 
  • Remove any solid objects that may be blocking the pipe and causing debris to stay inside. Move the heater if needed.

3. Loose Combustion Air Wheel

You can get an Atwood RV furnace 3 flashes code meaning ignition failure because your blower’s combustion air wheel is hanging loose.


Solving this issue is pretty simple. All you need to do is reposition the combustion air wheel and secure it tightly. Reset the heater and the error message should be gone.

4. Defective Circuit Board

A heater with a defective circuit board can show a lot of problems and error messages including an ignition lockout.

If this is what’s wrong with your heater, fixing the issue is going to be comparatively costly.


Inspect your control board. Burn marks or a bad smell are an indication that the control board is damaged.

Check whether power is going into the control board and coming out of it as it’s supposed to. If you detect that the board is faulty, you need to replace it.

Contact Atwood customer care to send you a replacement control board. At the very least, they will walk you through the process of where to get the control board and which model.

You can hire a licensed electrician to assist you with control board replacement. Or, watching the video will be helpful for you if you want to do the task by yourself.

5. Bad Heat Exchanger

A bad heat exchanger can cause an Atwood RV furnace ignition lockout fault. A heat exchanger usually has two heating components. Without this part, your heater will be unable to heat.


Follow the instructions below to replace a heat exchanger.

  • Remove the access panel to the heat exchanger. You will need to unscrew several screws with the help of a screwdriver. 
  • Once you can access the heat exchanger, take note of where the connections are made. Take a picture so you can easily figure out how to reattach it. 
  • Remove the fittings from the heat exchanger with the screwdriver and wrench. You should be able to pull out the heat exchanger rather easily once they’ve been removed.
  • Place it to the side while you install the new heat exchanger. Begin replacing and tightening the fittings as needed. 
  • Replace the panels and switch the power back on once the new heat exchanger is installed. Before it can operate, the system will require time to prime itself.

6. Low Voltage

Your furnace may not be getting an adequate voltage supply. You need a 120 V supply to run your Atwood furnace.


Check that the power outlet your heater is connected to is marked 120 V. Use a multimeter to see how much power your heater is getting.

If it is inadequate, call your local electric company to figure out what’s wrong. 

7. Blocked Burner Head or Orifice

Another common reason behind an ignition lockout fault on an RV furnace is a blocked burner head or orifice.

Over time, with use dirt, debris or grease can accumulate in your burner head. The dirt prevents ignition. Thus, an ignition lockout occurs.


You need to clean your furnace’s burner head and orifice. Here’s what to do. 

  • You need to turn off the power and gas supply to your heater, Access the burner, and remove it. Then starts the actual cleaning.
  • Clean the end of each burner facing the combustion chamber with a small brass wire brush. 
  • Blow compressed air through the opposite end of the brush to dislodge combustion byproducts inside the burner, then brush again until all deposits have been removed. 
  • Make sure debris is blown out of the burner’s fins on each side. The flames flow through these fins, allowing each burner to light up. You can use a can of compressed air if you don’t have an air compressor.
  • Replace the burner assembly and reassemble your heater. 

8. Broken Thermostat

When your heater’s thermostat is faulty, it can prevent ignition and cause an ignition lockout.


Test your thermostat with a multimeter first. You should be getting a reading of zero Ohms or as near to zero as possible. If not, your thermostat is faulty and needs replacement. 

We recommend you hire a trained electrician to replace your thermostat. But in case you have good electrical knowledge and are comfortable with working on appliances, you can DIY replace the thermostat.

9. Faulty Flame Sensor

A failed Atwood furnace flame sensor will not detect the igniter’s flame and burner gas valves won’t open in time for ignition. This results in an ignition lockout.


You need to inspect the flame sensor with a multimeter first to see if it is functioning. If you get a reading of 5-10 µA, that means the flame sensor is okay. Otherwise, replace the flame sensor.

  • Turn off the power and gas supply before locating the flame sensor. Unscrew and take off the access panel to get to the flame sensor. 
  • Disconnect the sensor’s electrical wire leads. At the control box, remove the other end of the leads. Using a nut driver or wrench, loosen the fastening screws on the flame sensor and remove it.
  • Install the replacement flame sensor in the same location as the old one and tighten the screws. Reconnect the sensor and control box’s electrical leads. Check to see that the furnace turns on and off properly.
  • Put everything back in order. Reset the system and the code should clear up.


What does the limit switch do on an Atwood furnace?

The furnace blower component is activated and deactivated by the furnace fan limit switch. This component is in charge of distributing warm air throughout your home’s air ducts. Furthermore, the furnace limit switch is designed to shut down the furnace if it becomes too hot.

Why is my furnace clicking but not turning on?

You most probably have a bad flame sensor if you can hear the igniter clicking but the burner won’t turn on. Test the flame sensor with a multimeter. If you get a reading outside of 5-10 µA, replace it.

What does the sail switch do?

The detection of fluid flow and the measurement of fan speeds are two applications for sail switches. A sail switch can prevent an electric heating element in a central heating system from being turned on before the airflow from the blower has been established.

How to reset an RV furnace?

To reset the furnace, look for the reset button on the heater. Look inside the blower compartment, the reset button is commonly at the side of the motor. Be cautious because the housing could be really hot. Press the button.

How do I know if my limit switch is bad?

The continual running of your furnace’s blower is the most prevalent indicator of a faulty limit switch. When the air reaches a specified temperature, the limit switch turns off the blower. A broken switch will not be able to do so.


Hopefully, you will be able to fix your heater with our instructions. In case you have questions about other Atwood furnace fault codes as well, you can comment below. We will get back to you soon.

About David

David is a man who loves doing research and finding out the best solution to any type of heating appliance issues like heaters and fireplaces. Whenever he finds the perfect solutions to any issues of heating appliances after doing in-depth research, he loves to share them with his readers. In fact, his aim is to help his readers to fix the issues with their heating appliances easily.More about us .

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