I have a 1986 mercedes model 300SD and am having some strange problems:

1. My outside temperature sensor reads 125 degrees or more independent of the outside ambient temperature - what's wrong?

2. My instrument panel is driving me wild. The symptoms are:

a. The coolant temperature gauge normally reads approx. 83 degrees C and is steady once the car has warmed up. However,
lately after normal engine warm up, it jumps up and down every second or so between maximum permissable operating engine temperature and the normally operating value of 83 degrees. The engine never overheats and there is plenty of coolant. Is it possible that the thermostat is thermally cycling between open and closed and needs to be changed?

b. When this happens, the fuel gauge, which would normally be steady, jumps up and down in sync with the temperature gauge movements.

c. If either turn signal is turned on, the temperature and fuel gauges jump up and down wildly in sync with the turn signal flashing signal intervals.

d. If the headlights are turned on, both turn signals flash in sync similar to the way the hazard lights would perform. The dashboard lights go out and the speedometer lights go off. The headlights stay on during all of this weird activity.

e. I was told previously that it looked as if I had a grounding problem. I had my mechanic check the car from one end to the other and he could not find any grounding problems. Help!