Truma traumas

[TheFrenchConnection]

I'd appreciate some help and opinions on this problem please. Sorry for the long post.

We have a diesel-fuelled Truma D6 hot water/heating boiler which is showing error E100H shortly after the heating is started. Typically this error code does not appear in any of Truma's lists. It can be restarted once the error code is cleared and the system re-initialised but fails again shortly after. Hot water works fine on its own and only shuts down when the heating goes into Error.

Our local Truma engineer  here (we're in Spain at the moment) is baffled. He carried out a lot of testing (eliminating the thermostat - an early suspect) but found that several similar codes suggest 'replacing the control board' so after long phone conversations with others he ordered and replaced the main PCB. Unfortunately to no effect. We're moving on soon so we've had to leave things there.

Since then I've been doing some empirical tests and come to some conclusions:

The error only occurs when the heating is started. Hot water is otherwise fine. Conclusion - the boiler is OK.

Very little air comes from the vents before the error message

The error still occurs if the heating is set to 'Vent' with no heat. Conclusion - nothing to do with heat, must be circulation.

Some Googling shows a replacement circulating fan with a smaller fan at the back cooling a control PCB - deduction, is this the 'board' that needed changing?

I'd appreciate anyone's comments on the error and my deductions. If I'm on the right track has anyone replaced the fan (it comes as a kit with motor and board) because, as normal, it comes with the usual admonitions that it should only be fitted by trained specialists!

Thanks for any help.

[TheFrenchConnection]

Should have added that, as in my previous post, the 12v circulating motor was mentioned in a reply from Truma but didn't seem to come up in our engineers tests while everything else pointed to the 'board'. I didn't know about the other 'board'!

[Derek Uzzell]

This December 2020 forum thread discussed replacing the air circulation motor of a gas-fuelled Truma "Combi" and I'm guessing that the task would be similar for a diesel-fuelled Combi D6.

https://forums.outandaboutlive.co.uk/topic/50925-truma-combi-air-circulation-motor-replacement/

(I've no idea if the task would be practicable in your case with the heater remaining in situ.

[TheFrenchConnection]

Thank you Derek, that's very helpful. I think I have room, but like everything it's going to be a fiddle.

I appreciate you're not a heating expert but does my diagnosis make sense to you?

[Derek Uzzell]

17 hours ago, TheFrenchConnection said:

...Some Googling shows a replacement circulating fan with a smaller fan at the back cooling a control PCB - deduction, is this the 'board' that needed changing?...

From your description above I think what you are referring to is the COMBUSTION motor unit, not the CIRCULATING motor unit.

The combustion motor unit is as advertised here

https://www.leisureshopdirect.com/gas/caravan-gas-water-heater/truma-heaters/truma-combustion-motor-for-combi-boiler 

and it looks like this

 

The combustion air fan will be running whenever the heater's burner is operating and (logically) the fan that cools the PCB will also be running simultaneously. 

This link describes how a Combi works

https://www.truma.com/uk/en/faq/function-truma-combi-heater

and I assume the speed of the combustion air fan(s) varies according to how 'hot' the burner's output needs to be. So a fault with the PCB MIGHT allow the combustion air fan-unit to operate acceptably when hot water only is being heated, but not when warm-air is required and a greater burner output is needed. However, this is just crystal-ball gazing and - in your case - the only way to prove whether replacing this part will provides a fix is to replace it and see what happens.

[Derek Uzzell]

It's perhaps stating the obvious, but - although a Combi D6 closely resembles a Combi 6 externally (and seems to have a combustion air fan-unit in the same place) - the D6 is a Truma/Eberspacher hybrid with a a different burner to the gas-fuelled Combi 6 and quite likely a different combustion air fan-unit, different PCBs, etc.

[TheFrenchConnection]

6 hours ago, Derek Uzzell said:

the D6 is a Truma/Eberspacher hybrid with a a different burner to the gas-fuelled Combi 6 and quite likely a different combustion air fan-unit, different PCBs, etc.

Thank you, I think your quote solves the confusion, the units do indeed look similar but there seems to be significant differences. Although the Leisure Shop Direct link states the unit is for the Combustion Air, the diagram in the documentation which came with with our D6  calls the louvered intake simply 'Circulated air intake' with a very similar fan assembly and a separately labelled combustion air intake (which is piped to the external intake/exhaust fitting). There is no separate combustion fan listed. This link https://www.jacksonsleisure.com/caravan-motorhome/spares/truma/spare-combi-e-air-motor-kit/ although listed as for  Combi E looks remarkably similar but is simply called 'Air Motor Kit'.

I think a detailed call to Truma's UK helpline is called for!

Many thanks for your interest in this, and for all  your research and help - it's so useful to able to bounce ideas around.

[Derek Uzzell]

This link may be useful

https://www.leisurespares.co.uk/spare-parts/heating-water-systems/caravan-heaters-truma/combi-and-combi-d

Although the combustion air motor kit (Part Number 34020-0235 and shown on the link you've provided) seems 'right' for a gas-fuelled Combi, the equivalent part for Combi D heaters has a different Part Number (34020-87900).

[TheFrenchConnection]

Thanks again, very useful to have such detail when I call Truma!