MR Heater Flame Problem [7+ Easy Solutions]

Seeing the flame on your MR heater, you can quickly determine whether the unit is functioning correctly or going through an issue.

Your MR heater flame problem signals that your heater is not operating correctly or something is wrong with it. However, the flame hitches you can come across are:

  • Too big or too low flame.
  • The flame keeps going out.
  • Orange or yellow flame. 
  • The heater’s flame is not coming up.
  • And the incorrect pattern of flame. 

Now, throughout our guide, we will explore the all reasons behind your heater’s unusual flame and their solutions. So, let’s started…

Table Of Contents

MR Heater Flame Problem [7+ Easy Fixes]

In this part, we will explain the different types of flame problems of your MR heater and their solutions: 

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

1. Heater Flame Up

Noticing the sudden big flame on your MR heater is not an unusual thing. While using your heater often, you can come across this issue. 

mr heater flame up 

However, the too-large flame quickly soots around your heater and can cause other fire-related dangers, carbon monoxide poisoning, and fuel running out too fast. Anyway, the potential causes of big flame in your heater are: 

  • Clogged gas in the air tube or improper gas and air mixture. 
  • Overloaded fuel tank. 
  • Too high incoming gas pressure. 
  • Clogged burner. 
  • Faulty gas regulator. 

How To Fix:

High flame on your MR heater can cause much damage. Therefore we recommend you immediately adjust your heater’s flame. If adjusting the flame doesn’t change the situation, you must clean the air tube properly and bleed the clogged gas. 

Dealing with gas is dangerous. Thus if you are not experienced enough, it’s better to contact an expert to bleed the gas.

The other thing that you must ensure is proper air and gas mixture in your heater. Make sure the gas pressure is not too high. Also, remove the burner’s dirt or debris build-up. 

Finally, when following all these ways you fail to solve the trouble, we recommend you inspect and replace the defective gas regulator. 

2. Low Or Slow Flame

When your MR heater gas regulator detects abnormal or unusual propane flow, the regulator will reduce the gas release amount. And thus, your heater’s flame becomes weak, and your heater produces low heat. This is another major MR heater flame hitch. 

mr heater low or slow flame 

The probable reason for the low flame on your heater is a kinked gas hose, improper air & gas mixture, and lower fuel on the propane tank. Lower fuel leads to inadequate gas pressure, which is another cause.

Moreover, sometimes your heater can get low gas pressure due to the defective gas regulator. 

However, gas can’t reach your heater due to the blocked burner orifice or pilot tube, and the unit produces a low flame. Again, dirty gas pipes and poor flame adjustment are the other culprits to blame. 

How To Fix:

A heater with an unusual fire can cause different dangerous situations. Therefore when your MR heater produces a low flame, we recommend you to immediately adjust the flame. 

Then check your heater’s gas hose and perfectly straighten it. Another important thing you have to do is to ensure proper air and gas mixture in your heater. 

Next, move forward, inspect and refill the propane tank and ensure your heater is getting sufficient gas pressure. We recommend you clean the blocked tube so that your heater gets sufficient gas.

Finally, check your heater and all other parts, like the pilot tube, gas regulator, and burner orifice. Then replace the bad one. 

How To Adjust MR Heater Flame

Whether your MR heater flame is too high or too low, you need to adjust the flame for your heater’s smooth operation.

For adjusting your MR heater flame remove the pilot adjustment cap. At the gas valve knobs below, this cap is located. Now to ensure a good size flame, adjust the pilot key. 

3. Flame Keeps Going Out

When you turn on your MR heater, your heater starts functioning and produces a deep blue flame. But sometimes after running for a few minutes, your heater’s flame keeps blowing or going out.

Or when you release the knob, your heater’s pilot flame doesn’t stay lit. This is really an irritating situation. 

However, your heater’s flame is going out, maybe the fuel tank is empty or the fuel is not sufficient enough. Or probably the control knob is not completely depressed in the “Pilot” position.

Also, some more reasons are the pilot flame not surrounding the thermocouple, defective pilot assembly, or the disconnected tip switch wires. 

How To Fix:

Your heater can’t function properly when its flame keeps going out frequently. So, to solve this problem, you must first ensure that your heater is getting proper fuel. Check and refill your heater’s propane tank and ensure there is sufficient fuel. 

Secondly, ensure you completely depress your heater’s control knob in the “Pilot” position. Then, your next task is cleaning the pilot and ensuring the pilot flame surrounds the thermocouple. 

Lastly, check your heater’s pilot assembly and tip switch wires. Replace the malfunctioning pilot assembly and connect the tip switch wires. 

4. Heater Orange Flame

When your propane-powered MR heater fails to burn the gas completely, your heater will produce an orange flame. 

MR heater’s ideal flame color is blue. And your heater’s orange flame through the combustion process produces carbon monoxide and gives you the danger signal. The causes of producing orange flame by your heater are:

  • Incomplete combustion. 
  • Dirty burner. 
  • Inappropriate air & gas mixture (Too much gas and insufficient air mixture).
  • Thermocouple’s mixed signals cause excessive gas release. 
  • Rust particles or iron in the gas flow or debris in the gas pipeline. 

How To Fix:

Your MR heater’s orange flame can come in the form of a short-lived spark or a big orange flame. And this flame indicates that dust or rust has stirred up in your heater. So check your heater’s burner, nozzle, and pilot light for dirt and adequately clean them. 

However, the most crucial thing you have to ensure is that your heater is combusting properly. Make sure the burner is receiving sufficient air. Now, the other effective fixing ways of the above troubles are: 

  • Clean the burner’s dirt and air inlet blockage and properly adjust the air inlet. 
  • Make sure your heater is getting the appropriate gas and air supply. 
  • Replace the faulty thermocouple.
  • Clean the gas pipeline and ensure nothing is mixing with fuel and reduce the gas pressure.

5. Heater Yellow Flame

A normally functioning MR heater will produce a deep blue color flame. But sometimes your heater may produce a slight yellow flame where the main burner flame and pilot flame meet. 

mr heater yellow flame 

However, the yellow color means your heater is facing a flame problem. When you fail to clean your heater correctly, dirt and debris build up in your heater, and it causes a clogged orifice that encourages yellow flame. 

Improper oxygen ratio for combustion or incomplete combustion and dust particles building up in the burner cause yellow flame.

Some more culprits to blame for this hitch are imperfect air and gas mixture, burner being out of adjustment, dirty burner or clogged air inlet, etc. 

How To Fix:

After turning on your MR heater, if you see the flame becoming more yellow than deep blue, we recommend you check the burner first. Periodically during use, visually inspect your heater’s burner and pilot flame. 

Using the air compressor blow the burner’s dirt and adequately adjust the burner. Also, ensure proper air and gas ratio for your heater’s complete combustion.

Finally, make sure the pilot flame is blue in color and extends beyond your heater’s thermocouple. 

6. Incorrect Flame Pattern

The wavering, flickering, or irregular flame pattern is your MR heater’s other flame problem.

The incorrect flame pattern in your heater fails to touch the thermocouple, and the thermocouple becomes cool. Thus your heater shuts down and can’t operate with the wavering flame pattern. 

So, a flickering flame gives you the signal that your heater is wasting energy. However, your heater’s flame operates in an irregular pattern for the following reasons: 

  • Excessive distance between thermocouple and flame. 
  • Improper gas pressure. 
  • Lower fuel supply. 
  • Clogged air hole inlet. 

How To Fix:

Solving the above troubles is easy. First, ensure your heater’s flame is touching the thermocouple. Also, make sure there is not much distance between the flame and the thermocouple. 

Afterward, check the gas tank and refill it if necessary. Then ensure proper gas supply & gas pressure. Also, don’t forget to clean the air inlet clog 

7. Flame Does Not Come Up

So another major hitch that you may encounter is that the flame does not come up or your heater won’t light.

When your heater’s gas burner turns off and fails in the gas build-up, your heater starts malfunctioning. As a result, the flame fails to come up. The other reasons responsible for this trouble are: 

  • Empty fuel tank.
  • Dirty or faulty pilot light. 
  • Malfunctioning temperature sensor (thermocouple).
  • Filthy burner. 

How To Fix:

When your heater’s flame fails to come up, the thermocouple will interpret this as a flame problem and force the gas valve to shut. However, to get rid of this hitch, follow the solutions below: 

  • Refill the propane fuel tank. 
  • Clean the pilot tube and burner’s dirt. 
  • Replace the malfunctioning thermocouple and defective pilot tube. 


Why does my MR heater make a whistling noise?

On a low setting, your MR heater makes a whistling noise mainly due to improper functioning, excessive gas pressure, or unusual gas flow. 

How does a thermocouple get damaged?

A thermocouple gets damaged due to metal fatigue, or the unit is exposed to extreme conditions or stress. The damaged thermocouple results in unusual temperature readings. 

Why is my propane heater not getting gas?

Your propane heater is not getting gas mainly due to the blocked pilot tube, filthy or defective thermocouple, overfilled/empty gas canister, and distance between the thermocouple and flame. 


Hopefully, now you know which type of MR heater flame problem you may face, their causes, and solutions. If your heater produces an abnormal flame, fix it immediately by following the ways mentioned above. 

However, if you have any other queries on the MR heater flame, let us know in the comment box. We will come to you ASAP with a possible solution. 

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 .

4 thoughts on “MR Heater Flame Problem [7+ Easy Solutions]”

  1. My blue flame Mr. Heater will suddenly flare up with a yellow flame and then burn down quickly to a blue flame again. It seems to only do it when the thermostat turns the heater back on. How do I fix the problem ?

  2. Hi Sir, My Mr. Heater does not shut off via the thermostat. The flame will go very low but stay on. It will also have a running flame and a popping noise as if it leaking lightly. There is no odors.

    • Hi Albert

      First, inspect the thermostat wheater it is ok or not. If not fix it.

      Then, adjust the flame & ensure the proper mixture of the air & gas.

      Plus, make sure the gas pressure is sufficient.

      Finally, check your heater and all other parts, like the pilot tube, gas regulator, and burner orifice. Then replace the bad one.

      And to know how to adjust flame check out “how to adjust MR Heater flame” in the article.

      Hopefully, your heater issue will be solved.

      Best of luck!


Leave a Comment