rugbyred

Hi I have a Berlingo 1.9d 600 1999. It has a few probs with elecs and yes, clock is one of them. When turning ignition to heat glow plugs they trip out at the relay, I think there is a bad earth somwhere as I have tested the plugs and leads and these are all ok. I have also checked the relay and this seems to be ok also. I am just about to resolve an issue today with the brake lights, when applied my front side lights are coming on as well. Heater switch no longer works so I have wired it direct to the battery as a temporary measure with an isolate switch in the cab so it only works on 1 setting (FULL ON). Has anybody got a clue as to my first problem as this getting annoying. It only does this on occaisions so the earth problem sounds about right. It seems to be dragging the battery down so not enough power to heat the plugs so they just trip out. Any suggestions will be welcomed Thanks Steve