1986 BMW 325 temp gauge

There is a nut holding the gauge to the circuit board inside the instrument cluster that often gets loose and the fuel gauge suffers from this issue as well. If you want to remove the cluster and tighten the nuts, drop the under dash and there is a plastic strip below the cluster that is retained by two thumbscrews accessible through the under dash, then remove the screws at the top of the cluster and wiggle the cluster out. You may wish to remove the steering wheel to ease egress. You can also inspect the service interval board at this time to see if it is in need of replacement, you can tell by the condition of the batteries, if they are leaking replace the board. Repost if you need anything else.