Looking for a bit of advice off someone with a problem with my gas hob rings been an ongoing problem for a while now but went into the van this morning to check a few things conected water and put hot water on gas everything fine as it should but the gas hob only had a small flame and when i turned the other rings on the flame got weaker also the glass cover must have a safety swith on it cos when i pushed the lid back a bit the flame got stronger on the rings let it go a fraction and the flame got a bit weaker any advice as to what the problem could be ??