Patio heater won't stay lit
I had this same problem - here's how I fixed it...
First: Never modify the safety features of your heater as has been suggested elsewhere on this forum. Modification of these features may allow the heater to work, but greatly compromises the safety of anyone near the heater.
The problem with the heater shutting off is most likely due to not enough gas flowing through the pilot orifice (this orifice is almost as small as the diameter of a human hair). When this happens, the pilot flame does not burn vigorously enough to activate the thermocouple. Hence, the thermocouple shuts off the gas and the burner goes out - usually you'll hear one "click" when this happens.
This is a maintence thing - meaning you may have to do this as a seasonal activity.
Here we go....
(1) Shut off the gas at the tank - or remove the tank entirely.
(2) Remove the screws that hold the burner shield and top shroud from the unit - set it aside.
(3) Remove the control knob - it just pulls straight off.
(4) Remove the panel immediately behind the knob you just took off. This will expose the gas valve assembly.
(5) Remove the cover that encloses the bottom of the pilot light/igniter (assembly). This will expose the bottom of the pilot assembly.
(6) Remove the screw holding the pilot assembly - there is a small hex nut on top, but under the burner that you'll have to hold to prevent it from turning. This will free the pilot assembly allowing you to gently pull it out of the pilot assembly housing. DON"T pull hard or you may break the gas line or thermocouple.
(7) Remove the hex nut that attaches the gas line to the pilot assembly and gently pull the gas line out. At this point, to ensure you have gas flowing through the pilot gas line, you may want to re-attach the gas tank, turn it on, gently move the gas line as far away from the spark ignitor as possible, temporarily replace the control knob, and turn the knob to the "Pilot" position & push it in. DO NOT DO THIS ANYWHERE NEAR AN OPEN FLAME OR A LIGHTED CIGARETTE! You should be able to hear a hissing sound as the gas flows. If you do not hear it, the problem may be with your gas valve, and if that's the case, I'm sorry this procedure likely won't solve the problem.
(8) Remove the pilot light tube (orifice) from the mounting bracket. There's a hex nut on the back side that holds it in. Be careful not to damage the hex nut or the threads. You'll need a pair of pliers (to hold the bracket) and an adjustable wrench for the hex nut. Make note of the orientation of the pilot burner diverter so you can put it back together the same way it came apart.
(9) Using a blast of compressed air, blow air through the pilot orifice. You should be able to see just a very (and I mean very) small pin-point of light through the pilot burner. If not, use a single strand of very fine wire - like one strand from a 18 gauge braided electrical wire - and run it through the pilot orifice. Carbon build-up can clog this orifice - which can prevent the pilot from burning vigorously enough to heat up the thermocouple. Cleaning it out periodically will likely solve the problem.
Put everything back together in reverse order as noted above - making sure your gas fittings are tight and don't leak. Once it's all back together, light the pilot flame as normal and once the thermocouple heats up, the heater should work like a charm.
