Water heating problems

I have not used my gas-driven water heater for some time and cannot start the heater up by gas. I have checked all the obvious things, but can anyone suggest something I may have overlooked, such as another gas valve, or something similar. I intend to do more wild camping this summer and won't be near electric hook-ups so I will need this working reliably.
Thanks, Elvereater

Go for basics:
1. is there gas working elsewhere in the van?
2. is the gas supply to the heater turned on?
3. when you turn on the heater can you hear the igniter clicking as it tries to light the pilot?

Mine has a safety switch on the roof window above the heater.
If the window is open or the switch faulty the appliance won't work.
Also be sure the outside cover is removed.

How long have you kept trying? It can take literally minutes to purge the air out of pipes that have not been used for a long time.

OK - I know there shouldn't be any air in a sealed system, but there always is when you come to light it for the first time in ages.

Dave

Thanks Gromit,

I have switched it on and off several times leaving 10 minutes between each attempt. I will try again.
The switch allows you to move from electrical mode to gas. According to the manual a green or red light is supposed to come on when you switch it to gas supply; red for failure and green for good. I cant get any light to show at all, so I was wondering whether that means either the unit is damaged or maybe a fuse has gone.
Any thoughts?
Thanks for your help

Elvereater

Ken Jones

Thanks for the comment on the safety switch. I will check it. Maybe thats the reason why I cannot get a light at all on the switch.

Elvereater

Steamdrivenandy

Q1.and 2 yes. Q3 No I cant hear any clicking at all. 
Any ideas what next?

Elvereater

If there's no clicking then it's not even attempting to light itself which means the electrics that activate and monitor the boiler when on gas aren't being activated. The lack of an indicator light suggests that too. So the problem isn't gas but is electric. Fuses, switches etc are all options.

SA Andy

Thats what I am starting to think. I notice there is a switch for the heater near the main fuse board so I assume this must be it. 
Many thanks for your prompt reply. If you dont hear from me; big thanks.
Elvereater

Have you turned the master switch on for the 12 volt side ? you probably have but worth asking the question.
Pete

Have you switched the unit OFF totally. On mine if any supply (12V, 240V or Gas) fails for ANY reason and is then restored th eunit stays off until the swithch i sturned off and then on again. Good safety!

Do you have a switch on the window above the flue? I tried for 3 days to light ours last year only for the ayatollah to ask if the switch on the window made a difference. I now hear about it every time I turn the water on.

THanks Guys for the help.
I have sorted the problem. The prize goes to Paul, although thankfully I found it before the Ayatollah. Although the top window was shut the rubber connector between the slider and the catch had become twisted and this was just enough to prevent the contact unit from closing. Its a bad design this because when you open the window the rubber connector has to twist as the angle of the window increases and eventually it starts to wear.
What I was amazed about though was that the unit started heating first time even though I had not used it for 2 years! Auto-sleeper get most things right with a little help from our German friends.
Many thanks for all your comments
Elvereater