It is on a 99 f-250 7.3 liter diesel I have checked all the wiring and can't find anything grounding out as soon as i turn the switch it blows the 30 amp fuse and the glow plug light goes off and it shuts down all the lights on the dash panel
any wire that is connected to that fuse and is grounded after that switch is a potential culprit. You could use a wire diagram to follow the circuits affected. I would check around the starter motor.
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