Just a suggestion if the pilot comes on you may be knocking the thermocoupler out of pilot flame alignment when replacing the cover. As you may be aware the thermocoupler is the safety cut out device, if the pilot goes out the gas is automaticaly switched off at the appliance gas valve.
I am only interested in you and your families safety by mentioning the following.
Gas appliances should only be serviced by Corgi registered fitters competent in mobile home appliances and signed off with a certificate. YES it does cover caravans and motor homes. Adding to mains electrics is covered also by Part P. You can do it but has to be signed off by a part P reg electrician.
Bob
June 2008