Truma error code - 255-help!

[The Ryans]

Hi there we’re away in our motorhome at the moment (2020 Zefiro) we have no heating with error code W255H. Red LED light on combo tried resetting on control panel and on the dipswitch on boiler
Still won’t reset pretty sure there is 12v at the boiler as it lights up
Any ideas much appreciated
Regards
Cold John and Tina near Brighton

 

[Miggs]

It's usually a lack of power to control panel issue so have all relevant fuses been checked?

 

[pwilmo]

Hi I had this fault also, it made me think there was no gas getting to the boiler, it would fire up but then cut out ..bought and fitted new regulator.

Still had the fault, I had to to reset the boiler down at the plastic clip off casing, the red light indicator has to go off if you do it right.

Reset on panel and all worked.
This was my experience this may help.
Good Luck

 

[matbic]

W255H in digital control panel or no device detection after reset | Truma Serviceblog

serviceblog.truma.com

 

[The Ryans]

Thanks for all your help. Not had chance to sort it yet but will let you know when we managed to fix it and how

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[The Ryans]

Thanks PWilmo and Marnix for messages
Unfortunately fault still on MoHo error code W255H with occasional W621H
Have checked the 13 fuses in distribution board and the one on the heater circuit board all ok with meter
Have 14v at heater on large red and black cables and believe the data communication is ok as when I disconnect plug the red and green LEDs stop flashing.
Did find loose wire on starter battery fuse but this didn’t resolve the fault
The reset button doesn’t alter the red and green flashing unfortunately
Any more ideas much appreciated
Regards John

 

[irnbru]

I would suggest unplugging the control panel for a minute then plug it back in.

 

[The Ryans]

Hi Irnbru…..Have disconnected all the plugs at the boiler and reconnected no luck did you mean the Truma inet control box?

 

[Carolyn and Kev]

Service und Support

support.truma.com

Take a look at this to see if it helps you any more.

Kev

 

[irnbru]

Hi Irnbru…..Have disconnected all the plugs at the boiler and reconnected no luck did you mean the Truma inet control box

Yes a lot of times it will reset if you disconnect from control box. Give it a try.

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[GeoffnDee]

There should be another 12v fused permanent power supply to the control which would be worth checking ,

 

[The Ryans]

Thanks GeoffnDee
Have only 3 of the 6 wires from control box to heater with continuity in the data cable would have thought they all should be?
There are 3 pairs of cables going to the boiler only the heavy cables have batt volts
Sounds like I have lots of cables failed or I am chasing my tail on this one!
Regards
John

 

[GeoffnDee]

It does seem to be a possible data cable ( RJ12) fault which would also match the W255H fault code which can be for a loss of connection between heater and control panel (It can also indicate loss of 12v supply to the boiler , but that seems ok)

 

[pwilmo]

Sounds like you've done a comprehensive job checking all the wires and fuses, I know zero about motorhome electrickery.

When I cleared the red light flashing, 2 or 3 presses didn't work, but long presses on the red and it eventually reset to green.

The boilers on our Rollers are very reliable and rarely at fault, as a last resort persevere with the red reset button.

 

[matbic]

Thanks GeoffnDee
Have only 3 of the 6 wires from control box to heater with continuity in the data cable would have thought they all should be?
There are 3 pairs of cables going to the boiler only the heavy cables have batt volts
Sounds like I have lots of cables failed or I am chasing my tail on this one!
Regards
John

The normal Truma data cable only has only 3 wires connected. These are the 2 I know - there is also a 12v on one other - sorry not near my van so cant go and find out which pin it is on.

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[GeoffnDee]

The Ryans , If you still have a problem , have tried a replacement data cable and have confirmed that the separate 12v supplies to both the boiler and control panel are ok , it may be a problem with the PCB on the Combi , www.arelectronics.co.uk can test this for you if required .

 

[The Ryans]

Thanks all for support
Picked up new boiler PCB and problem is resolved…unfortunately the main control unconnected to heating seems to be playing up….looks like the on/off switch is intermittent as it won’t switch on/off and toggles other functions like lights pump etc…looks like I will have to get another PCB-could be a voltage spike has frazzled both
Will get there one day and hopefully get the girl out on the open road!

 

[The Ryans]

BTW Truma Burton will test a suspect PCB FOC before you buy another
Refurb £140 new £300