Truma Combi 4 not working

[GrannyT]

We'd be very grateful for any help with our Truma Combi 4 that we use for heating and hot water in our MH.
Normally to get the unit started, we turn the knob on the 'Truma Combi' rotating control panel (36011-01), and the grey 'fins' light-up yellow (or flashes), accompanied by a noise as the Combi 4 starts up. At the minute, nothing happens! No lights at all.

We have done the following:

• Checked the fuse in the Elektroblok - which is still looking good
• Checked the fuse in the Truma Combi 4 unit - also still looking intact
• Checked that power is getting to the Truma Combi 4 unit - and getting a reading of 13.1v
• Bought a new Truma Control Panel 'CP Classic' - made no difference (photo is of old one with trim removed)
• Checked water getting to the unit - which is is, as I can drain it through the unit via the dreaded blue diamond-shaped knob!
• Checked gas bottles are full - and they have plenty in, and we can run the Gas hob and Refrigerator
• 12v circuit seems to be working on everything else i the MH

Do any of you helpful Funsters know of what the problem could be, and how we go about fixing it please?
Thank you all - any help would be much appreciated.

 

[GeoffnDee]

The problem could be with the data cable that links the controls to the heater.
The CP plus control has an extra fused 12v supply to the display is that in place ?

 

[GrannyT]

The problem could be with the data cable that links the controls to the heater.
The CP plus control has an extra fused 12v supply to the display is that in place ?

Thanks for the reply, GeoffnDee. I think that the controller that we've got, being non-digital, doesn't have the extra fused 12v supply? We'll try a new Data cable though - so thanks for that suggestion.

 

[Gellyneck]

Thanks for the reply, GeoffnDee. I think that the controller that we've got, being non-digital, doesn't have the extra fused 12v supply? We'll try a new Data cable though - so thanks for that suggestion.

I could be wrong so await confirmation, or otherwise, but I'm pretty sure the Truma 4 uses a data cable with an "internet type" connection to the boiler and there are two sockets on the boiler (right-hand side of the boiler panel).

I believe both these sockets are for the same function (control panel / diagnostic) and are interchangeable so might be worthwhile trying to move the cable to the other connection first to see if that works.

EDIT: just remembered I've got a copy of the installation manual for it and fig 20 pg 18 seems to support the above (but at your own risk).