Mr Heater Contractor Series Won’t Light [Solved]

MR Heater Contractor Series won’t light mainly due to the inadequate fuel supply, malfunctioning, dirty or incorrectly installed thermocouple, filthy fuel filter, non-functioning pilot light, and blocked pilot tube.

If your heater refuses to light, be sure that any of these factors hinder your heater’s perfect functioning.

However, throughout this troubleshooting guide, we will explain the factors responsible for these problems.

Mr heater contractor series won't light

And we will also guide you to fix your MR Heater won’t light issue. So, don’t waste time and keep reading this guide till the end.

Note: It doesn’t matter Whether your MR Heater Contractor Series kerosene, diesel, or propane forced air heater, you can fix your heater won’t light issue following this guide.

Mr Heater Contractor Series Won’t Light [8 Easy Solutions]

The major causes for which your MR Heater won’t light and their effective solutions are:

Mr heater contractor series

Note: You can also read how to fix Reddy heater not igniting problem.

1. Insufficient Fuel (Propane, Kerosene, Diesel) Supply

Due to a lack of adequate fuel (Propane, kerosene, diesel), your MR Heater Contractor Series may spark, but it will not light. The causes of insufficient fuel supply in your heater are:

Mr heater contractor series insufficient fuel
  • A lower amount of propane gas, kerosene, or diesel in the fuel tank or empty tank
  • Dirty gas valves 
  • Inadequate or unadjusted air pressure or pump pressure
  • Dirt build-up at the fuel tank’s bottom
  • Dirty fuel filter
  • A degraded fuel line sucks air
  • Empty or overfilled drafts and gas canisters
  • Clogged or damaged gas flow restrictor valve (If the heater is gas fueled)


When your MR Heater Contractor Series suddenly stops lighting, you should check your heater’s fuel supply. And make sure your heater is getting sufficient fuel. The other fixing ways of the above troubles are: 

  • Refill your heater’s propane gas, kerosene, or diesel tank. Also ensure an adequate amount of gas, kerosene, or diesel supply
  • Using a needle, properly clean the gas valve (if the heater is gas fueled) and make sure it is appropriately supplying fuel
  • Adjust the fuel pressure and ensure the proper air pressure
  • Clean your fuel tank bottom’s dirt or carbon build-up and dirty fuel filter
  • Replace the degraded or damaged fuel line
  • Make sure your heater’s gas canister and drafts are not overfilled or empty
  • Properly clean the gas flow restrictor valve and replace the faulty one
  • Adjust or decrease the pump pressure 

2. Defective Or Dirty Thermocouple

MR Heater’s heat-sensitive safety device is the thermocouple which prevents the unburned gas’s release. Your heater’s pilot becomes light when the thermocouple signals the valve to stay open.

But when the thermocouple gets defective or dirty and fails to signal the gas valve to stay open and misinterpret the pilot light temperature, your heater won’t light or stay light. However, your heater thermocouple gets defective for the following reasons:

  • Bent, damaged, or broken thermocouple
  • Faulty extension wire of the thermocouple
  • Metal fatigue or deteriorated thermocouple
  • Thermocouples exposed to extreme conditions or heat stress
  • Loose or over-tightening thermocouple
  • Thermocouple unable to detect flame due to cad cell’s faulty wiring or dirt build-up 


When your MR Heater Contractor Series stops lighting or won’t stay lit, you should check your heater’s thermocouple. However, if the thermocouple goes bad, do the following to fix this hitch:

  • Replace the damaged, bent, or broken thermocouple, defective extension wire, & metal fatigued unit
  • Make sure your heater’s thermocouple is not going through extreme conditions or heat stress
  • Ensure the installed thermocouple is neither loose nor over tightened
  • Check and replace the CAD cell’s wiring
  • Properly clean the CAD cell photocell
  • Finally, clean the thermocouple if it’s dirty

Thermocouple Cleaning Tips

From your heater’s process assembly, remove the thermocouple. Then using emery cloth or steel wool, clean the tip’s end. Also, you can use sandpaper and gently remove the dirt or carbon build-up from the tip’s end. Clean the thermocouple, and your heater will light again.

3. Filthy Fuel & Air Filter

Grime accumulation on your MR Heater’s fuel filter is another reason why your heater refuses to light. The dirty fuel filter hinders fuel’s easy transmission to your heater and your heater fails to light.

Moreover, over time, due to lack of cleaning dirt accumulates in the filter. And dirt creates clogs or blockages in your heater’s fuel line.

Also, the dirty fuel filter causes the power switch wires to be damaged. Thus your heater fails to light due to the faulty switch or wire. The dirty and clogged air filter is also responsible for your heater not igniting.


If your MR heater doesn’t light, check its fuel filter. Then correctly clean the dirty filter or replace the faulty filter.

Also, maintain a cleaning routine so that grime can’t accumulate on the filter. Again remove the fuel line clog and make sure the line is transferring fuel perfectly.

Then open the air filter and clean it. If it’s too clogged and worn out, then replace it.

4. Incorrectly Installed Thermocouple

A thermocouple’s incorrect installation or installation too far from the flame is another reason why your MR Heater won’t light.

An incorrectly installed or slightly dislodged thermocouple fails to respond to your pilot light’s temperature change and your heater stops lighting.


For your MR Heater Contractor Series unit’s safe operation, installing the thermocouple correctly is extremely important. Follow the manual’s instructions during the thermocouple installation to ensure your heater’s flawless operation.

To correctly position your heater’s dislodged thermocouple, first turn off your heater. Wait a few minutes and make sure your heater’s internal components cool down sufficiently. Manually move your heater’s thermocouple closer to the flame and in its original position.

5. Non-Functioning Pilot Light

Pilot light malfunction is one of the main reasons why your MR heater Contractor Series stops lighting. The pilot light is your heater’s small flame.

After turning on your MR heater, the unit releases gas to the main burner. And thus your heater turns on when the pilot light ignites that gas.

Now, if this pilot light becomes faulty, it will not ignite the gas, and your heater won’t light. The causes of the pilot light’s malfunction are:

  • Incorrectly located pilot light
  • Dirty pilot orifice
  • Cracked heat exchanger or heating element
  • Lack of enough combustible air
  • Broken or bent thermocouple
  • Faulty sensor

If your heater is gas fueled, the following factors are also responsible for pilot light issues.

  • Bad gas regulator
  • Clogged gas flow valve 
  • Fluctuating gas


When your heater refuses to light, you should check whether your MR heater’s pilot light is functioning perfectly or not. Inspect the pilot light and make sure it is not going out frequently. However, if it is the culprit, do the following to fix it:

  • Make sure the pilot light is correctly positioned
  • Replace the faulty gas regulator, lousy sensor, broken or bent thermocouple, cracked heating element, or heat exchanger
  • Ensure enough combustible air in the pilot light
  • Make sure your MR heater’s gas pressure is not fluctuating and properly clean the gas flow valve blockage (For gas fueled heaters)

6. Blocked Pilot Tube

Your MR Heater’s pilot tube is a very narrow tube. Due to a lack of proper cleaning and maintenance, dirt is trapped in this tube. And then the blocked tube hinders your heater from lighting correctly or causes a flickering or yellowish flame. 

However, Gas, carbon, spider web, or other minor foreign objects can create blockage in your heater’s pilot tube.


You will get a small viewing window close to your heater’s control knob. From the window try to view the pilot flame. The yellow flame means the pilot tube is dirty and you need to clean the tube. 

Using a sharp thin object like a paperclip or needle, clean your heater’s pilot tube. While cleaning the tube’s clog, if you see it is damaged, you should replace it.

7. Leaky Air Hose

Another cause for which your MR Heater can’t light up is the leaky air hose. The air hose connects your heater’s air pump to the unit’s burner nozzle. But when this hose leaked, it failed to connect and caused unregulated air pressure.  

The leaked air hose will create a hissing sound. Or there can be a hole in the air hose. Don’t attempt to light your heater if you detect the leaky air hose. 


Check for your MR Heater’s air hose hole or hissing sound. If you notice these signs, replace the leaky or bad air hose.

8. Faulty Control Board

Your MR heater is getting proper air and fuel pressure and spraying fuel (Propane, Kerosene, diesel), but still, your heater is not lighting up. This means your heater’s control board is not functioning.  

Due to the high air pressure or defective high limit switch, your heater’s control board can go bad. Also, the loose or faulty igniter wires cause this board’s malfunction.


Check your MR Heater Contractor Series control board’s voltage before disconnecting the board’s igniter wires. Click on your heater on/off switch and turn on the switch. You need to check the control board’s voltage within 1-3 seconds of turning on the switch.

However, if the voltmeter is reading 120 volts that means the control board is functioning perfectly. But no voltage on the board means the board is defective. Thus, replace the faulty control board.


What does E1 mean on MR Heater?

Displaying E1 on your MR Heater control panel means the turned-on overheat sensor. When you unplug your heater, the overheat sensor will reset itself and show the E1 code.

How do I know if my thermocouple is working?

When your thermocouple functions, at the tube’s connection end, you can measure the voltage of 30-40 millivolts. Test the thermocouple using the multimeter when your heater pilot flame is on.

Why does my MR heater keep going out?

Your MR heater keeps going out mainly due to the pilot tube blockage, defective thermocouple, weak pilot, excessive distance between thermocouple and flame, faulty or incorrectly placed heat sensor, etc.

Wrap Up

Hopefully, now you have a clear idea of why your MR Heater Contractor Series won’t light. We explained the A-Z details of each factor, including their causes and solutions. 

However, If you have any more queries, don’t hesitate to let us know in the comment box. Soon you will get a reply with a solution.

About William

William is the founder of He has real life practical skills in fixing smoker & heating appliance issues. He loves to share his knowledge & helps others in fixing their appliances & saving their money. William firmly believes that anyone can repair his or her unit with the correct guidance & knowledge. See more at about us.

Leave a Comment