Well had a little trouble on our last outing, although the blow heating was working after a while it would cut out, when the fan started again it was blowing cold! As we wanted the heating to work during the night to keep the chill off this wasn't good, as in order to get heat again you had to take out the drawer above the fire to reach the reset switch!
Gary from Arc Systems was contactable through UK Campsite Forum Repairs and was able to advise that a build up of dust on the fan blades can often be the culprit. Not enough air passes through to regulate the thermostat and the safety feature is that it cuts out as it gets too hot and has to be reset. Just by cleaning the blades of even a little surface dust it can make a difference.
The tricky thing is reaching the MK1 fan on the back of the fire......
Two drawers above it are the only access to the back of the fire without removing it!! Well we took both drawers out and using a mirror and a torch we were able to identify where the screws were and started to remove it.
Getting it out was tricky due the electrical unit on the back and the fan motor which we had to half remove to tilt it through the opening. We removed the fan and I carefully cleaned it with cotton bud and mini brush - boy it was more than a thin covering.
Once cleaned, fan was reattached, fed back behind the fire and electrical unit back on and reattached.
Plugged electric cable in and hey presto warm air with no tripping for a few hours. So now we will be toasty on a night. All good.
Sorry no pics - should have done really just so you could see the dirt build up but was that keen to get it back in and working - didn't get any taken.