(84 300 SD, California version)
Im having trouble with an engine grouding problem. The temperature gauge keeps fluctuating, but when I take a wire from the engine block connected to the negative battery terminal, the temperature reads correctly and all fluctuations in gage stop. The problem is trying to isolate whats causing the engine block not to ground properly? Any ideas where to start? I tried disconnecting almost all the engine sensors and that didnt help. When I connect the wire it actually is producing a small spark on the engine block. Thanks in advance.