Re: Temp. Gauge...
Ground the "S" (send) terminal to ground. With the key on, the needle should peg hot. If not check the gauge for +12 volts and ground. If that checks out the gauge is probably bad. If the gauge pegs, it is ok. Next, ensure the send wire is good from the gauge to the sender on the engine. Continuity check is required for that. If that checks out, then check the sender resistance. Disconnect the wire at the sender and measure resistance from the terminal to ground. Engine cold it should read about 240 ohms (give or take a bit depending on ambient temperature). If you can, start the engine and watch the ohm meter as the engine heats up. Resistance should begin to drop. An overheated engine would read roughy 33 ohms. If resistance doesn't decrease the sender is bad. I'm guessing though that you have a bad connection. Since the temp sender wire is in the engine harness I suggest you disconnect, inspect, and clean the large engine harness plug. That connection may be corroded. Gauges are rarely the issue. Senders are next less likely, and wiring is most generally the issue.
