ProfJohnL said:
Helo Voldolan
The fact you have had to ask the question suggests you are not adequately familiar with gas appliances, which means there is not a great deal you can do to effect repairs without involving a trained fitter.
However if you have a look at this thread
http://www.practicalcaravan.com/forum/technical/50725-trumavent-heating
You will see some hint on how to check the ignitor. But beyond that I have to recommend you refer it to a dealer.
Hang on a minute, the OP asked for a possible reason why his fire was not sparking, which on Truma fires is almost always due to the igniter battery being flat, usually because the fire has not been serviced for a good time, or the owner has not switched the control knob off properly.
There is certainly no need for a trained fitter to replace the battery as it does not even involve removing the fire front to do, it is accessable from under the front left hand side of the fire and is a simple slide up panel and replace the AA battery.
If the fire THEN does not light, it is time to involve an engineer , if needed.