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 screws, 4 upper, 4 lower)
- remove 2 screws (right upper and left lower) of the Ammeter + Temp Gauge sub-cluster
- take this sub-assembly straight off (there's no more clips)
- carefully remove the 2 plastic clips to remove the cover of this sub-assembly
- remove 3 screws of the 2 gauges
- carefully remove temp gauge
- note polarity of condenser (the old one has arrows to PLUS! Nowadays, MINUS is shown on them), a photo with your smarty phone helps a lot. Cut wires of condenser short off printed circuit (leave a lead to solder a new one)
- carefully scrap clean the remaining wires (otherwise, soldering may fail)
- solder a new condenser with the same capacity (47uF, 50V is just fine) and obey the right polarity! (see above, take a picture)
- assembly in reverse order
LED goes on only, if coolant temp rises above a certain level (I tested only with my testing switch - with "full/hot" setting, it lights).
Be happy
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 screws, 4 upper, 4 lower)
- remove 2 screws (right upper and left lower) of the Ammeter + Temp Gauge sub-cluster
- take this sub-assembly straight off (there's no more clips)
- carefully remove the 2 plastic clips to remove the cover of this sub-assembly
- remove 3 screws of the 2 gauges
- carefully remove temp gauge
- note polarity of condenser (the old one has arrows to PLUS! Nowadays, MINUS is shown on them), a photo with your smarty phone helps a lot. Cut wires of condenser short off printed circuit (leave a lead to solder a new one)
- carefully scrap clean the remaining wires (otherwise, soldering may fail)
- solder a new condenser with the same capacity (47uF, 50V is just fine) and obey the right polarity! (see above, take a picture)
- assembly in reverse order
LED goes on only, if coolant temp rises above a certain level (I tested only with my testing switch - with "full/hot" setting, it lights).
Be happy