The red LED in my temp gauge was flickering all the time. The sending unit and the gauge tested just fine.
It turned out that after 40 years the condenser on the little printed circuit right behind the gauge (not the big one!) was gone. It obviously dried out and had almost no capacity. It's the gray part on the lower left on the last pic.
Following procedure to replace it - as there are 2 transistors, be careful with static charges to not kill them:
- carefully remove Dash bezel (8...
Fix temperature warning LED flickering - M-Body LeBaron 1979
