Thermix won't stay lit

[Northlander]

1975 Overlander, I can get the thermix heater to light by holding the pilot thing, but when I release it and wait a bit, nothing. Bad thermo coupler?

[loudruff]

Thermocouple corroded at contact point? Carboned up? Gas valve corroded and not being properly opened? Bad thermocouple? Could need cleaning in the air inlet which may be preventing the sail valve from opening. All of these things can be investigated for free if you are handy. Take it all apart, clean and put it back together. Retry. Good luck!
Go to the forums for furnace fixes and repairs...use the search function. You may find further pertinent research there.

[65CV]

I bet I'm not the only Mythbusters fan who thought -- after reading "Thermix won't stay lit" -- you need a blasting cap!

(The latest episode was about lighting plastic explosives)

[RickDavis]

I am assuming that you are referring to a thermix catalytic heater.
When you light it with the pilot flames will creep across the pad. After it has warmed for 20 or 30 seconds and you release the button the pilot will go out and so will the flames across the pad.
At this point it will continue to make heat but there will be no obvious flame. Sometimes a slight red glow might be seen in the dark.

If it is not doing this it could be a bad thermocouple.

[Northlander]

Took it all apart, cleaned, and checked the thermocouple. It checked fine. Reassembled, and lit it up. This time, I was very quiet and I could hear a small amount of gas going through after releasing the pilot and waiting, then setting control to high. There was a very small amout of heat coming off the bottom of the unit. When I listened closely, low, medium, or high didn't make any difference. I'm pretty sure there is a little bit of gas coming out, and it must be burning because I don't smell any raw propane. So now I' thinking control valve or plugged hole where the gas comes out. When I had it apart, I see that the gas comes out at the top of the unit and then just falls over the catalytic material and burns like that? I could put my hand right on the grill, and it wasn't too hot, just a bit warm at the bottom.

[azflycaster]

Sounds like a gas flow issue. The one in my trailer gets very hot and you can not touch the grade when it is running.

BTW, the propane does not burn. It is a chemical process with the propane and the platinum in the heater that causes the heat, but there is no flame.