welding precautions

Sounds like an area got too hot from the welding and might have melted through some wiring --- I would check the welded areas wiring harness real good as that should have been insulted from the heat with a welders blanket. Disconnecting the ground is good practice anytime electrical work or major work is being done but I don't think that caused your problems. Melted wires down to the wire touching the frame or another wire would be suspect in my opinion. A check you could also do would be to put an amp meter at the battery and see what kind of amperage is being pulled with everything off. Should be very minor -- 100 ma or less from things like a clock. More than 1 amp would be suspect. Hope this helps.