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Why Will My Propane Patio Heater Not Light?

We love sitting out on the patio under our propane heater in the evenings, but lately, it’s become a bit hard to light. What’s the main cause of this?

Propane patio heaters usually do not light due to a dirty thermocouple (the temperature sensor) or a dirty pilot light. This can be solved with a simple bit of cleaning rather than having to buy new ones. You also need to check if you’ve run out of propane, which is surprisingly easy to do.

Let’s dive down into this subject in more detail, and discover the main causes of propane heaters failing to light, and what you can do to stop it happening in the future by keeping your heater cleaned and well maintained (unlike ours!)…

What Causes a Propane Heater Not To Light? (Why Won’t My Patio Heater Light?)

There are several reasons why your propane heater is failing to ignite. Most often, it’s due to a problem with the thermocouple (the temperature sensor) or the pilot light. This can often be remedied with a simple bit of cleaning, and we’ll look into this shortly.

An even simpler reason is there might be a bit of a breeze, which is blowing out the pilot light. As your patio heater is, naturally, on the patio, it’s not unlikely that there’s air movement.

The igniter is also a potential issue. The easiest way to test whether the ignition is the source of the problem is to grab a stick lighter and light the heater manually. If this works, then the igniter may be dirty or worn out.

Also, check the valve and the hose between the propane cylinder and the heater. A dirty or blocked valve or a kinked hose will prevent the gas from coming through.

And we hate to sound patronizing, but we all always need to check this one… Have you run out of gas? That last bit of propane sure seems to run out quickly! 

Another potential issue is the outside temperature. Propane doesn’t like being below 40 degrees, and your heater won’t work at these temperatures.

So, we’re sorry, but there are a few things that you’ll need to check if your patio heater isn’t lighting. On the bright side, at least there are lots of fixes to try before you give up on your old heater. We’ll take a closer look at troubleshooting and solutions.

How Can I Clean The Igniter On My Patio Heater? (My Patio Heater Igniter Won’t Spark)

The igniter (or sparker) can be the cause of the problem. There’s a simple way to test for this: try lighting the heater manually with a stick lighter. If this works and the burner ignites, then the igniter is at fault.

These do get worn out with time and use, and they’re easy and cheap to replace. You can pick up a universal igniter online, or contact your patio heater’s manufacturer if you want to stick to the brand’s spare parts. 

You could always try cleaning the heater first. Disconnect the gas and remove the emitter screen, then gently use a straw brush or (preferably) compressed air to dust the inside. Never use a damp cloth, as the parts need to remain dry.

How Do I Test My Patio Heater Igniter?

If your propane patio heater won’t light, there may be a problem with the igniter. Most patio heaters have an igniter, which is also known as a spark igniter or a sparker. This is a small electrode that ignites the pilot light.

To test whether your igniter is the problem, try lighting your heater manually using a stick lighter. (If you haven’t got one, a match will do, although be extra-careful with your fingers in case the burner springs into life…). If the pilot light ignites when you use a manual lighter, then the problem lies with the igniter.

You can then take a closer look at the sparker. Remove the emitter screen (this is the screen around the main burner, and it’s usually easy to remove using a screwdriver). You can now get a proper look at the ignition assembly.

This is made up of the sparker itself, the pilot tube, and the thermocouple. You can carefully hold down the ignition switch and look out for a spark. No spark? It’s time to pick up a new igniter, an inexpensive part that is pretty easy to fit yourself.

How Do You Clean a Thermocouple On a Propane Heater?

The thermocouple is the temperature sensor on a propane patio heater. Like any sensor, if it’s not working properly, it can effectively stop the whole system from functioning. If the patio heater ignites OK but then won’t stay lit, it could be because there’s a problem with the thermocouple. 

The thermocouple is a simple copper rod that’s located next to the pilot tube, and together with the sparker, forms the ignition assembly. It’s a safety feature, and its role is to halt the gas flow if it doesn’t detect the pilot light, preventing gas leaks.

The thermocouple can easily become dirty, and this is usually caused by a build-up of carbon from the propane. This carbon coating covers the sensor. Because it can’t sense the pilot light through this layer of dirt, it assumes that the pilot light has gone out, and so shuts down the whole thing. Arguably, it’s still doing its job, but not in the way we want it to!

Luckily, the thermocouple can be cleaned. Disconnect the gas and remove the emitter screen (typically, this is held on with just a few screws). Again, you need to make sure that the inside of the patio heater stays dry. Use a small brush to clean away the carbon layer.

But what if this coating is too built up to remove with a brush? If you’re super-careful, you can use a small tooth file and lightly sand the carbon from the surface. Still not clean? It may be time to invest in a shiny new thermocouple for your heater.

Here’s a short (and strangely relaxing) film about how to change the thermocouple on a patio heater. 

How Do You Test a Patio Heater Thermocouple?

How do you establish whether the thermocouple is the problem? Well, if you think it may have a buildup of carbon that’s preventing it from working, take the emitter screen off and have a good look at it.

But what if it looks perfectly clean, and the patio heater still isn’t staying lit? You’ll need to check that the thermocouple is in the correct position.

The thermocouple works by sensing the heat from the pilot light. If it can’t sense this, it shuts down the heater by preventing the gas flow. Sometimes, this small copper rod can become dislodged (especially if it’s a portable heater and you’ve been moving it around) and moves away from the pilot light.

Now, the thermocouple is no longer close to the pilot light, and can’t sense its heat. It does what a good sensor is meant to do when it is triggered and closes down the system. The result? The heater ignites, then rapidly goes out again.

This can be a really quick fix. Switch off the gas and take off the emitter screen. Loom at the ignition assembly. Does the thermocouple seem to have moved, or look like it’s a long way from the pilot tube? 

Using a small pair of pliers, gently squeeze the thermocouple closer to the pilot tube again. This really is a simple fix.

Just bear in mind that there could be other reasons why the gas isn’t reaching the heater, such as a leak or twist in the hose, a clogged or faulty valve, or the gas has simply run out.

What to Do When Your Patio Heater Won't Light
What to Do When Your Patio Heater Won’t Light

How Do I Reset My Propane Heater? (How to Light a Patio Heater Manually)

After you’ve replaced an empty propane cylinder, you’ll need to reset your patio heater. After you’ve removed and replaced the empty tank, you’ll need to make sure that the pilot light is working safely again.

There should be a knob inside the heater that has a Pilot position. Push this in, then light the pilot using the igniter, as you usually would. Hold the knob in for about half a minute, which gives the thermocouple time to start working.

Release the knob. Has the pilot light stayed on? If it has, you’re back in business. Enjoy the cozy warmth on your patio.

Final Thoughts on Your Patio Heater Not Lighting

So it looks like all our patio heater needed was a good clean of the thermocouple and the pilot light, so we could get that propane flowing through it again and light it.

This is a bit of a lesson for me actually – and it serves me right for just leaving our heater outside for too long without cleaning it properly.

Oh well, we live and learn! 🙂

Mark H.

Homeowner and property investor Mark H. aspires to bring you the very best outdoor living content, based on his years of experience managing outside spaces. Read more >