erratic guages
 

The temp guage on my '84 300SD fluctuates wildly. When driving it will shoot up to 100 degrees and stay there. If I bring my fist slamming down on the dashboard (OUCH!) it will return to just above 80 for a bit then back up to 100. The dealer replaced the cluster and cleaned the contacts but the problem keeps happening. The engine temp is normal.:confused:

Just an idea--but check the ground contacts. Figure out where the grounds are for the instrument cluster and clean them up. An electrical diagram might help you figure out which ground to clean. A location diagram might help you to find the ground that you want to clean.