NCYankee wrote:
I would look for a common ground connection. A corroded ground can cause intermittent indications.
Maybe check he braid/cable grounding the engine block to the engine frame.
Txs, OK – going to inspect that. 
Yes it could be that.
Also I would carefully examine the wires going to the back of the alternator. They are not secured all that brilliantly and will be subjected to some airflow.
I would look for a common ground connection. A corroded ground can cause intermittent indications.
OK – I focus on that, however the voltage indicator doesn´t show more than 28.1 V, 28.2 V, 27.9 at the cigarette lighter. I assume a new Lamar 386-5 is the best choice. Could this habe been a reason for the erratic fuel gauge, too?
This is a schematic I have found from the POH
If you were asking about a Cessna, I’d be looking at the regulator and over voltage sensor as failure points. I simply don’t know of your electrical system has a similar design. I agree that if your alternator is producing electricity correctly at some times (when cycled), it is probably not the source of the problem. Cessna over voltage sensors are a system weak point, and voltage regulators are known to fail. If you would like to post the schematic of the electrical system from your flight manual, posters will be better able to offer suggestions…
