Why My MR Heater Won’t Light [9 Easy Fixes]

Your MR heater won’t light mainly due to the filthy pilot tube, insufficient fuel supply, malfunctioning temperature sensor, defective igniter, and faulty hose.

Also, the other responsible factors are gas valve malfunction, faulty pilot orifice, and clogged gas flow restrictor valve. 

However, by going through this ultimate MR heater troubleshooting guide, you will learn the exact causes and solutions of the above troubles. So, let’s get started…

Table Of Contents

Why My MR Heater Won’t Light + How To Fix

After hitting your MR heater’s start button, you may see the spark in it. But your heater’s pilot won’t light mainly for the following reasons: 

Note: You can also read how to fix Mr heater won’t stay lit problem.

1. Dirty Pilot Tube

A filthy pilot tube is one of the main reasons why your MR buddy heater won’t light. The defective or blocked pilot tube reduces the gas flow; thus, your heater fails to light. 

The pilot tube at its end has a small opening. Due to improper maintenance or cleaning, dirt or debris build up on this end. And thus, your heater doesn’t get the fuel to light. 


If your MR heater propane heater won’t light, you should first turn off your heater’s gas supply. Then check the pilot tube and adequately clean the dirty tube. 

How To Clean The MR Heater Pilot Tube

For cleaning your MR heater’s dirty pilot tube follow the easy steps below:

  • Turn off your heater’s gas supply 
  • From your heater’s gas control module, unscrew the pilot tube 
  • Remove the pilot’s debris by blowing the compressed air 
  • If any dirt or debris build-up blocks the pilot tube, using the needle, try to dislodge the tube’s soot 
  • Now properly wipe the pilot tube’s exterior and turn on the gas by reassembling your heater 

2. Inadequate Fuel supply

Your heater requires sufficient fuel to light and operate. Now, if for any reason gas fails to come out and the heater doesn’t get the power, the unit will not light at all.

empty propane tank 

However, your MR heater not getting propane gas for the following reasons: 

  • Lower fuel or empty propane tank 
  • Kinked hose 
  • Dirt or debris build-up or spider made a web in the fuel nozzle 
  • Inappropriate or too low gas pressure 
  • Faulty gas regulator 
  • Dirty gas valve 
  • The gas valve is in off position 


If your brand new MR heater won’t light, first you should check its fuel tank and make sure your heater is getting sufficient fuel to light. Now follow the ways below to light your heater by ensuring proper fuel supply: 

  • Refill your heater’s propane tank. Always refill the tank by 80%; otherwise overfilled tank can cause other issues 
  • Straighten the hose or replace the faulty hose 
  • Clean the dirt, debris, or spider web from the fuel nozzle and gas valve 
  • Ensure your heater is getting appropriate gas pressure 
  • Replace the defective gas regulator 
  • Make sure the gas valve is in the On position 

3. Defective Temperature Sensor (Thermocouple)

Your MR heater fails to light due to the malfunctioning thermocouple or temperature sensor. The defective temperature sensor fails to detect the heat, and the gas valve shuts down.

Mr heater  temperature sensor

Thus your heater won’t get enough gas supply to the light. However, your MR heater’s temperature sensor becomes bad for the following reasons: 

  • Too much distance between the thermocouple and the flame, and the heater is not getting any gas 
  • Dirty or clogged thermocouple 
  • The thermocouple dislodged slightly from its original position 
  • Worn-out, broken, or damaged thermocouple 


The heat-sensitive safety device is the thermocouple, and it prevents unburned gas release. But when the faulty thermocouple senses the wrong temperature, it shuts off the gas supply and thus your heater will not light. 

Try to light your heater manually. If it lights, that means the lousy thermocouple is hindering your heater from lighting. Thus replace your heater’s bad thermocouple and follow the ways below to fix the above troubles: 

  • Reduce the thermocouple and flame’s high distance and ensure the thermocouple is within 2/3 inch of the flame. 
  • Properly clean the thermocouple’s dirt 
  • Placed the thermocouple correctly in its original position 
  • Replace the broken, worn-out, or faulty thermocouple 

4. Malfunctioning Igniter

The defective igniter very often fails to cycle long enough to light your heater’s propane gas, and thus your MR heater won’t light.

Due to the igniter malfunction, the burner gets no gas, or gas fails to enter the burner, & thus your heater can’t light. However, your heater’s igniter becomes defective for the following reasons: 

  • The heater is getting a high-voltage supply of electricity 
  • Overusing the heater 
  • Excessive gas valve pressure 
  • Defective control board 
  • The overheated heat exchanger damaged the igniter 


Manually light your MR heater. The faulty igniter is the culprit if your heater lights up manually or works fine. Thus you need to replace the malfunctioning igniter. Also, for solving the above troubles, follow the solutions below: 

  • Make sure there is no electricity frequency variation and your heater is getting the correct voltage 
  • Avoid overusing or frequently turning on and off your heater 
  • Reduce the gas valve pressure 
  • Replace the faulty control board and overheated heat exchanger 

5. Faulty Hose

Hoses connect your MR heater to the fuel source and allow the gas flow to power or light up your heater. But the defective hose prevents your MR heater from lighting up by hindering the gas transfer from one point to another.

However, your heater’s gas hose can be faulty when it becomes worn out, broken, or damaged over time. 


Replace your MR heater’s defective hose and make sure your heater is getting proper gas flow to light. 

6. Defective Gas Valve

The gas valve supplies the necessary fuel in your MR heater pilot light, and your heater lights up using this fuel.

But the faulty gas valve doesn’t allow the gas to flow to the burner trays and without a gas supply, your heater doesn’t light. Your heater’s gas valve becomes faulty mainly for the following reasons: 

  • A damaged or worn-out gas valve or valve stops functioning properly 
  • A glitch in the safety circuit 
  • Worn-out thermocouple 


The faulty gas valve prevents your heater from lighting up and can cause a gas leak. Thus you should immediately check your heater’s gas valve and replace the faulty one. The other fixing ways are: 

  • Replace your heater’s worn-out or damaged valve and defective thermocouple 
  • Make sure the valve is functioning perfectly 
  • Remove the safety circuit’s glitch 

Gas Valve Replacement Instructions

For replacing your MR heater’s malfunctioning gas valve, follow the instructions below: 

  • Turn off your heater’s gas supply 
  • Near your MR heater’s burner, find out the gas valve 
  • Unscrew the valve from its place 
  • Using a dry cloth piece, properly clean the valve’s area 
  • Install a new gas valve in the position of the old one and tighten the valve’s screw

7. Pilot Orifice Malfunction

The main job of the pilot orifice is to control the gas flow toward your heater’s pilot. The faulty pilot orifice can’t control the gas flow, and your heater doesn’t get adequate gas to light.

Mr heater pilot orifice

Usually, the pilot orifice becomes defective when it becomes broken, damaged, or dirty. 


Check your MR heater’s pilot orifice and ensure it is controlling your heater’s gas flow perfectly. And replace the faulty, broken, or damaged orifice. Also, properly clean the orifice to ensure proper gas supply to your MR heater. 

8. Igniter Electrode Issue

Ignition electrodes are used for the gaseous fuel ignition in your MR heater gas combustion equipment. Due to the following igniter electrode problems, your MR heater cans stop lighting. 

  • Incorrectly positioned igniter electrode 
  • Defective igniter electrode 
  • Broken, moist, or pinched igniter cable 
  • No connection between the igniter and igniter electrode 


Your MR heater igniter system’s component is the ignition electrode, which produces a spark in your heater. Different issues with the ignition electrode hinder your MR heater’s lighting up. Thus you need to fix the problems above following the ways below: 

  • Ensure your MR heater’s igniter electrode is correctly positioned 
  • Replace the faulty igniter electrode and the broken, or pinched igniter cable 
  • Ensure proper connection between your heater’s igniter and igniter electrode 

9. Clogged Gas Flow Restrictor Valve

Just before your MR heater’s pilot light, the small gas flow restrictor valve is located. And this valve controls the gas flow pressure.

However, the clogged gas flow restrictor valve can’t ensure proper gas flow to the unit, and thus your MR heater’s big max won’t light

Due to improper cleaning, dirt and debris build up in the valve, and the valve gets clogged. 


If your MR heater stops lighting, you should check the gas flow restrictor valve to ensure the proper flow of gas to your heater.

However, properly clean the clogged valve and remove its dirt following the steps below: 

  • Turn off your MR heater’s fuel flow 
  • Carefully remove the gas flow restrictor valve from its position 
  • Now using either a needle/pin or compressed air, carefully clean the valve 
  • After cleaning the valve, place it again properly 


Why does my MR heater make a whistling noise?

Your MR heater is whistling because of the low gas setting or inappropriate gas flow. The whistling sound gives you the signal that your heater is not working perfectly. 

Why is my MR heater keep shutting off?

Your MR heater keeps shutting off mainly due to the defective or dirty thermocouple, clogged pilot tube or pilot orifice, and too much distance between the thermocouple and the heater’s flame. 

How do you adjust the pilot on an MR heater?

You must remove the pilot adjustment cap to adjust your MR heater’s pilot. Below your heater’s gas valve knob, the pilot adjustment cap is located. Now adjust the pilot key to ensure proper flame size. 

Wrap up

So, now you are aware of why your MR heater won’t light. If your heater refuses to light, you will now detect and fix this issue by yourself at home in no time.

Don’t hesitate to comment if you fail. Our expert will help you to resolve your heater’s issue. 

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 .

Leave a Comment