any advice on hoe to get my hot water to light, i always have problems getting it to STAY lit, i bleed all air out remove the vent cover and purge the gas and light it lights but goes out after 10 sec try again and again sooner or later it will work, also does my caravan hot water only work on gas i dont have any instructions. The caravan is a 2004 elddis avante 534.Any tips or help appreciated.