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.

 

[gary]

Late to party but you've already wasted the cost of thermocouple and chances of magnet failure are slimmer still!
Truma don't suffer corrosion issues on thermocouples connection which is only cause of thermocouple issues and magnet is similar so my first check is control rod fully pushing the pair together when pushing down. Ensure cleanliness and free operation of valves shaft

 

[Hutch]

Late to party but you've already wasted the cost of thermocouple and chances of magnet failure are slimmer still!
Truma don't suffer corrosion issues on thermocouples connection which is only cause of thermocouple issues and magnet is similar so my first check is control rod fully pushing the pair together when pushing down. Ensure cleanliness and free operation of valves shaft

Thank you Gary, you are always helpful.

 

[IanB1485]

Can you see the thermocouple tip glowing red/orange? , if not then the holes in the mantle may be partially blocked so the flame is too high also high pressure in the gas line can cause to the flame to be too high and not warming the thermocouple enough.You can test the thermocouple using a thermocouple tester ,search amazon or ebay for " Thermocouple Tester tool for testing Gas thermocouples" With the S3002 its a two person job, one underneath with the tester and one holding the gas valve open and igniting the pilot, you can also test the old one by holding it in a flame

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[trevormonty]

This maybe of help. Different heater but principle is same. Electricity generated by thermocouple operates a valve. If you do ohms test of valve coil shouldn't be open circuit. Looking pictures think magnet insert is solenoid valve.

View: https://youtu.be/7m5ZDvOoVwU?si=JAz-RuDaizzvtzlE


I had similar problem with fridge turns out there was bad connection in switch that selects between, 12V, 230V & gas. Gas position should connect thermocouple to valve solenoid.

 

[IanB1485]

This maybe of help. Different heater but principle is same. Electricity generated by thermocouple operates a valve. If you do ohms test of valve coil shouldn't be open circuit. Looking pictures think magnet insert is solenoid valve.

View: https://youtu.be/7m5ZDvOoVwU?si=JAz-RuDaizzvtzlE


I had similar problem with fridge turns out there was bad connection in switch that selects between, 12V, 230V & gas. Gas position should connect thermocouple to valve solenoid.

Yes I've come across that on old dometic fridges ,I had to strip down the switch assembly and clean the contacts , The low voltage and current allows debris to build up on the contact surfaces.The difficulty with the Truma S3002 is the thermocouple and gas valve connections are all under the caravan and the best way is to completely remove the unit from the caravan and bench test it , but this requires a suitability equipped engineer and workshop

 

[trevormonty]

Removing fridge to overhaul switch is a mission. Easy option is just run on gas and don't touch switch. We are offgrid most of time so its gas more often than not.

 

[IanB1485]

No , just pulling it forward allows access to the switch. I have a block of wood which supports the back of the fridge whilst pulled forward.