Troubleshooting A Propane Heater That Won’t Stay Lit 

It happens pretty often. You light the propane heater or furnace. It runs for a few minutes then goes off. Then, hoping it’s just a minor issue, you relight it. But, again, it stays on for just a few minutes before going off. 

What could be the problem? 

Why Does my Propane Heater Shut Off After 5 Minutes

Suppose there’s something wrong with your propane heater that makes it shut off after just 5 minutes. In that case, it’s usually because of insufficient gas supply, a malfunctioning thermostat, corroded flame sensors, or the flame sensor is off.

Insufficient gas supply

There’s no way the furnace will stay ON if the gas supply is insufficient. That’s because the modern furnace is designed such that it only stays on if certain gas pressure is met. Below the defined point, the unit will go off until the pressure level is met. This can cause the furnace to go ON and OFF repeatedly.

Insufficient gas supply can be due to leaks, blocked gas lines, or an empty propane tank. You can fix an empty propane tank yourself. However, you need professional help for the other two cases. 

The pressure switch is off

Speaking of gas pressure, furnaces also have special monitoring mechanisms designed to cut the gas supply if the pressure keeps fluctuating. The pressure switch, for instance, monitors venting pressure and will shut the gas supply if venting problems are detected.

Venting issues often result from serious issues such as a cracked exchanger or blocked exhaust flue. Both of these require professional intervention. 

A corroded flame sensor 

Besides regulating gas supply to the pilot, the flame sensor also directly regulates gas supply to the burners. It stays ON for as long as the furnace is ON, keeping an eye on the flame, and will cut the gas supply when it detects that the flame is gone.

However, if you have a malfunctioned flame sensor, it may fail to detect the burner flame, even if one is present, thus cut off gas and consequently shut off the furnace. 

Unfortunately, there’s no one right answer. Sometimes the propane heater may struggle to stay lit because of wind. On an extremely windy day, the fast-moving air can blow out the heater within minutes of lighting it – and do so repeatedly until the wind calms down. 

However, it may also be a severe issue, such as low gas supply caused by gas leaks. In this case, you may need to shut off the gas supply at the valve and call an HVAC professional. 

Below, we discuss the main reasons why a propane heater may refuse to stay lit, along with probable solutions. 

Propane Heater Pilot Light Won’t Stay Lit

Before we get to burner issues, let’s consider a scenario where the propane heater can’t even light up in the first place because the pilot light keeps going off. The pilot light can go on and off repeatedly for many reasons, including;

The thermocouple is bad

The thermocouple, also known as the lame sensor, is a copper rod that determines the presence of a flame and allows or shuts off gas supply depending on the presence of a flame.

By doing so, it guards the home against the catastrophic buildup of poisonous gas as well as prevents potential fires. We’ll discuss more thermocouples later. However, you may need to clean or replace it if the pilot light keeps going out. 

The pilot light is dirty

A dirty pilot light can also go on and off repeatedly. Remember that the pilot light uses very little gas supply. Therefore, even a little dirt can block the gas passage, rendering the pilot ineffective.

A weak flame due to dirt buildup may not envelop the thermocouple completely, causing the flame sensor to return a negative answer. Fortunately, it’s easy to clean the pilot light. 

The gas regulator is bad 

The gas regular controls the amount of gas entering your home from the main supply. If it’s malfunctioned or compromised, it may not send enough gas to your furnace, potentially causing the pilot light to go on and off repeatedly. It would also impact actual heating. Fixing a bad gas regulator is best left to the experts. 

Propane Heater Keeps Shutting Off

If the propane heater keeps shutting off, perhaps at shorter intervals, you should still g back to the three potential issues above, i.e., gas supply, the pressure switch, and the flame sensor. 

Propane Heater Thermocouple Problems 

We’ve already mentioned that the thermocouple is a small rod that monitors the furnace flame to regulate gas supply. We’ve also seen that it will keep the gates open for as long as a flame is present and shut off the unit immediately it loses track of the flame. 

However, the thermocouple can malfunction, too, causing the furnace to go off even if the rest of the furnace is in excellent working condition. So, what could go wrong, and what can you do about the potential issues?

  • A dirty thermocouple: The thermocouple could become dirty, thus lose its flame sensitivity. This may render it unable to detect a flame even where one is present. 
  • A damaged thermocouple: A thermocouple can break, or some of the wire may become loose. When this happens, the flame sensor may lose its flame sensitivity.
  • A dead thermocouple: If the furnace has been in use for a long time, it may be dead due to natural wear and tear. 

There are a couple of ways to verify that your furnace thermocouple is dirty, damaged, or dead. However, we recommend the following three-step process. 

  1. Inspect it for discoloration and cracks: Discoloration and cracking are usually the first signs that you have a compromised flame sensor. A damaged thermocouple may also have pinholes. 
  2. Check for wiring issues: A damaged or compromised thermocouple may have loose, worn, or corroded wires. Also, check for missing insulation and bare wires. These are other signs of trouble. 
  3. Inspect it for physical damage: The thermocouple comprises a tube, brackets, and wires. Physical damage to any of these components may hinder the flame sensor. 

Testing the flame sensor 

If you identify a couple of issues, or even if you can’t point any issues outright, but the thermocouple still won’t work, you can test it to verify its functionality. Proceed as follows;

  1. Turn off the gas supply at the gas valve to prevent poisoning and avert potential fires. 
  2. Unscrew the copper lead and connection nuts, then lift the bracket nuts to remove the thermocouple. 
  3. Check your multimeter by touching the two leads together with the multimeter set to ohms (resistance) reading. The meter should read zero. Now you can turn back the multimeter to volts.
  4. Now, turn ON your flame source and place the tip of the thermocouple in the flame, leaving it until it’s very hot. 
  5. Attach the multimeter leads to the thermocouple. The first lead wire goes to the thermocouple side, while the other goes to the part that typically goes into the pilot light.
  6. You should get a reading between 20mv and 30mv (millivolts). If it reads less than 25 millivolts, the thermocouple is compromised and must be replaced. 

Other Reasons your Propane Heater Won’t Stay Lit

Aside from the above issues, you also want to troubleshoot the following issues for a propane heater that refuses to stay lit. 

Dirty Pilot Tube 

The pilot tube which brings gas to the pilot light may become dirty and effectively block gas flow to the pilot light. For instance, spider webs, carbon, and dirt can build up in the tube, thus blocking it. 

Fortunately, you can clean the pilot tube in a few simple steps as follows;

  1. Turn off the propane heater completely
  2. Soak a soft sponge in warm detergent water
  3. Using the soaked sponge, gently wipe the top of the heater

If there’s excess dirt around the area, use a microfiber towel to wipe it off. The towel will also wipe off excess water in the area. 

Draft Problems 

Draft issues are also a common reason why the furnace may struggle to stay lit. This can be a major issue depending on the furnace’s placement. For instance, it’s near impossible to avoid draft issues when using a propane heater outdoors. 

The only viable solution is to cover up the heater with a canopy or sunshade. A wind barrier, such as a tall wall, may also do the trick. Otherwise, you may have to bring the heater inside. 

Electronic Spark Mechanism Issues 

Although we’ve already covered ignition issues, we want to stress the possibility of electronic spark ignition issues. If the electronic spark ignition system has any problems, your furnace may produce little or no heat. It may also cycle frequently or cause the blower system to overreact. 

We strongly recommend that you leave electric spark ignition issues to the experts. Avoid DIY as the electric spark system is extremely delicate. 

Gas Cylinder May Be Empty

Finally, a propane heater that refuses to stay lit may also signify low fuel or an empty tank. Fortunately, refilling an empty propane tank is a simple, straightforward process. Just make sure to purchase your refill from an authorized dealer. 


Hopefully, you now know how to troubleshoot and fix most issues that may cause your propane heater not to stay lit. But, remember always to call the pros as soon as you exhaust your DIY ideas.