The night heater on my volvo fh has stopped working and I am unsure where to start looking for a problem.
When you press the button on the dash then the light comes on to say it’s working but that’s all that works. There is no noise from a relay or the pump and nothing coming from the fan.
What should I try looking at first?
when was it last used
Most days but in this case I think it was on Saturday
Friend of mine has a problem with his on the new model he switches it on then removes the fuse,then sticks it back in seems to cure it.
same eact problem on 2 of our volvo fh units, did the usual checks, intake hose blockage, output blockage, batteries ok, not a vacuum in the tank. started out as the heaters trying to start, blowing for one cycle but not putting out heat then stopping and not going again, now they’re both light on, but nothing happens. Probably needs a mechanic/sparky looking at them.
Ok thanks I will look into it a bit more and see what it might be and see if I can get someone to have a look. I see the fuse is hidden below the first level so need to take that out first.
I will put a post on when it’s fixed and say what the outcome is
might just need a service etc on it.
Volvo night heaters are cack,always on the blink 
Glow plug
kindle530:
Glow plug
+1
How old is the truck, does the central locking work?
I had the same problem with my 2007 fh light on switch but nothing else, I was also having problem with the central locking blowing fuses. Turns out there some circuit and black box that’s used to operate equipment not used with the keys in the ignition, such as central locking and night heater. This unit was shorting out which was blowing the central locking and meant that the night heater didn’t work.
In fact I posted the problem on here and somebody said they share a common circuit.
kindle530:
Glow plug
I think with things like glow plugs problems or blockages the heater will try to fire up, but will then stop running if it doesn’t kick in.