I have a quick question about what ground the dash lights use. the problem is when i turn on the turn signals on my 92' sc400 the dash lights on the cluster and heater unit will dim when the turn signal flashes. i know its some kind of bad groud but im not sure which one. If any one has a elec. diagram handy please help me find the ground and which colored wires im looking for. thanks

 

All SC's do it to an extent. You don't need a diagram to clean your ground, just clean both ends of the negative cable.