Truma Heater Issues This Winter

On Tuesday (20/12/2022) we started packing our caravan ready to take to our daughter’s for Christmas. 

As a precaution I decided to check that the heater and hot water were working. 

When I turned on the heating (Truma combi manufactured around 2017/2018) I got an error code W255 H. A look at the manual advised that this suggests a loss of the 12 volt source. 

I took off the top half of the cover to the circuit board and checked the power to the unit and measure 12.8 volts, thus suggesting a different problem.  Until the error code is cleared the heating will not operate,  so another look at the Truma website suggested a reboot. 

This can be done in one of two ways according to the year of manufacture. One method is to disconnect the 12 volt supply and leave it disconnected for about half an hour but on the more recent models there is a reset button,  but to access that you need to remove the lower cover. 

I spoke to a caravan service technician and he said that when the lower cover is removed with the 12 volt supply connected,  there should be a flashing led which goes steady once the board has been reset.  Horror of horrors,  no flashing led but loads of water. 

I spoke to the techy again and he said that he wasn’t surprised about the water and that it would stop the circuit board working.  He said that with a bit of luck if it is dried out carefully it should be alright. I put a fan heater in the caravan on a low heat for 3 hours and when I went back to check,  to my amazement and delight the circuit board was dry and the led illuminated and the error code clear.  It seems that what happened was associated with the rapid change in temperature from -6 degrees on Monday to 14 degrees on Tuesday,  the body of the heater cooled down and then the warmer air caused the condensation to form.

I am offering this advise in case anyone else has a similar problem.  I was surprised that this happened as we keep a dehumidifier in our caravan which runs for about 4 hours every night.