Trume Ultraheat 3002 pilot light

[Swift Mark]

A
Hi All, My first post on here.
I've been caravaning for over 20 years and am a maintenance engineer.
I have a Truma Ultraheat 3002 and the pilot light wont stay on, a new thermocouple has been fitted but it still goes out as soon as the button is released, even when held down for over a minuet.
Could this be the magnetic insert (Truma part No 190) ?

 

[ProfJohnL]

Truma never used to sell the electromagnetic hold magnet separately. I assume that will still be the case. It was always an integral part of the gas valve assembly. In practice the hold magnet is usually very reliable.

I presume the heater would not stay alight with the old thermocouple hence it being changed. Perhaps it was not the thermocouple at all. as that is still the case with the new TC other causes need to be investigated.

Its unlikely the position of the thermocouple will change as its fairly well protected by the heat exchanger, so its more likely the flame is either the wrong size, or its not burning correctly.

Flame size is dependant initially on the gas supply pressure ( is it correct check the heated data plate for the correct operating pressures, ) but flame size can also be reduced if the burner is partially blocked which can both reduce the gas air pressure/velocity under the flame grill, but it can also cause the gas flow to be misaligned, leading to incomplete mixing with air in the venturi, producing a yellow sooty flame.

 

[Swift Mark]

Thanks for your reply John.
Yes that is why I changed the thermocouple.
The flame is nice and blue, and visually the same as it's always been.
The thermocouple is indeed mounted securely and doesn't show any signs of movement (past or present).
I have found the hold magnet for sale separately at a few suppliers for around £30, the van is now 20 years old, so I'm not surprised it's starting to have a few faults.