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.