It seems that the temp guage is erratic. I first noticed that it would be very erratic, jumping (like an audio vu meter) on first start and then would settle down, it seemed, at running temperature (just below half). Now, at cold start, or even just pre start, it is at half and quickly jumps to a far hot as possible, especially if I turn on the headlights. I can turn the headlights on and off (or any of the electrical units, but headlights create most "load")and the guage jumps back and forth. The engine is not running hot. Any help deeply appreciated. If something needs to be replaced (sensor,etc.) please tell me where it is located. Thanks so much.

My 1989 740 turbo did the same thing and it was the temp sending unit. On the b230ft it is on the left side of the cylinder head in the middle. On the 6304f-s its on the very back of cylinder head.

THANKS TO BOTH.. I WILL CHECK IT OUT.

Most likely a bad wiring connection: take each one apart, clean, protect with silicone grease, and reassemble.