Why Your Patio Heater Won't Stay Lit

You hold the knob in, the pilot catches, you count to thirty, you let go, and the flame dies. Try again, same thirty seconds. Or it runs five minutes over a table full of people and then quits on its own, in the cold.

When a patio heater won't stay lit, the burner is rarely the problem. The fault sits in the safety chain, the parts that cut the gas the instant they stop being satisfied there is a flame. One of them has stopped being satisfied, and it is usually right to do so. Five causes, in roughly the order they turn out to be responsible.

Before you touch anything, turn the gas off. Close the valve on the propane tank, or the shut-off on the natural gas line, before you go near the pilot assembly, the thermocouple or any fitting, and let the head cool. If you loosen a gas connection at any point below, you leak test it with soapy water before you relight. Those steps are in the sequence that follows. Do not skip past them.

When a patio heater won't stay lit, start at the thermocouple

A thermocouple is a heat sensor: the thin copper coloured rod whose tip sits in the pilot flame, wired back to the gas control. Heat the tip and it makes a tiny current, and that current is the only thing holding the pilot gas valve open. Let it cool and the valve shuts, which is the design working, not failing. A heater that dies the moment you release the knob is telling you the thermocouple is not making enough current. Three reasons.

It is dirty. Soot and a season's grey scale insulate the tip, so it sits in the flame but never gets hot underneath. Gas off, heater cold, cover off the pilot assembly, then rub the tip with fine sandpaper or a soft brass brush. Dull clean metal, not a polish. It is the most common free fix here.

It is out of position. The pilot flame has to wrap the tip, covering roughly the top half inch of the rod, not lick past the side of it. A flame sitting beside the thermocouple never gets it to temperature, and the valve closes right on schedule. Ease the bracket back in small movements: a rod bent hard once will not survive being bent back three times.

It is finished. If a clean tip in a correct flame still will not hold the valve, replace it. Thermocouples are consumable and inexpensive: match the old one's length, thread and connector.

Fitting a new one is a spanner job.

1. Gas off at the tank or supply valve. Disconnect the propane tank and let the head go cold.
2. Open the pilot assembly, photographing the layout before anything comes out.
3. Unthread the thermocouple nut at the gas control, free the bracket, then fit the new rod in reverse order. Snug the nut, then a light quarter turn: overtightening ruins new parts in their first minute.
4. Leak test before you relight. Reconnect the tank, brush dish soap and water over every connection you loosened, open the tank valve slowly with the controls closed, and watch. Bubbles mean a leak. Gas off, fix it, test again.
5. Relight with the head open to the air, standing to one side. Never lean over the burner while you hold the knob in.

The tilt switch, the check people skip

Nearly every freestanding patio heater carries an anti-tip switch, and so do most mounted ones: a small sealed device that cuts the gas the moment the heater is off vertical. On decking, or on a slab that has settled over the winter, that is easy to trigger by accident.

Check it before you buy a single part. Put a level on the post in both directions, and load the base the way the manual intends: an underweighted heater rocks in gusts and trips the switch every time it does. A heater dragged across a patio can also knock the switch loose or pull its wire off the terminal, which looks exactly like a dead thermocouple.

Wind, draft, and where the heater is standing

A steady draft across the pilot will either blow it out or cool it enough that the thermocouple gives up, which is why the same heater behaves perfectly in October and hopelessly in November.

Most burner heads have a wind guard around the pilot. If yours is missing, crushed, or was left off after a clean, refit it. Then look at siting: the gap between a house wall and a fence funnels wind harder than the open yard, and moving the heater a few feet often ends it. A gas grill in the same weather follows nearly the same order of checks: see why a grill igniter clicks but will not light.

The gas side: a low tank, a tripped regulator, a spider

A low tank. Propane has to vaporize inside the tank to feed the burner, and a nearly empty tank on a cold night cannot do it fast enough. The heater lights, runs a few minutes, then starves, and swapping in a full tank is the fastest test there is.

A tripped regulator. Regulators trip a safety device if the tank valve is opened quickly with a control already on, and then pass only a trickle: enough for a pilot, not enough to hold a burner. Turn everything off, disconnect the tank, wait a minute, reconnect, then open the tank valve slowly with the controls closed.

A spider in the pilot tube. The seasonal one, and it is real. Insects nest in gas tubes over the summer, and a partly blocked pilot orifice gives a small lazy yellow flame that will never hold a thermocouple. Clear it with compressed air, and never drill an orifice: that changes the gas flow rate permanently.

When it is the valve, stop

If the thermocouple is new and correctly placed, the pilot is strong and blue, the heater is level, and the gas supply checks out, the remaining suspect is the gas control valve behind the knob. That is where do-it-yourself work should stop: the valve carries full supply pressure, it is model specific, and one that has been apart is not something to relight over a table of people. Order the correct assembly for your model, or price it against a new heater.

Frequently asked questions

Why does my patio heater go out after 30 seconds?
Thirty seconds is roughly how long the pilot valve stays open after you release the knob, so a heater that dies right there never had the thermocouple take over.

Why does my patio heater keep going out after a few minutes?
Minutes rather than seconds points away from the thermocouple and toward the gas supply or a draft. Check the tank level and the wind guard first.

How long should a thermocouple last?
Several seasons in normal use. They fade rather than fail outright, which is why a heater that has turned fussy in the cold is often running an ageing one.

Getting the part, or the heater

Thermocouples, pilot assemblies and control valves are model specific, so find the model plate first, on the post or inside the base. Then browse patio heaters and the wider outdoor heating range, or go straight to a brand: AZ Patio Heaters for freestanding propane and natural gas units, Bromic for mounted gas and for electric infrared, which has no pilot to lose in the first place.

Weighing another part against a new heater? How to choose an outdoor heater that actually works covers sizing and mounting.

Free shipping on orders over $75. If the model plate has faded, photograph the burner head and the control knob and call 1 (866) 850-3450, and we will identify it with you.