Dear all, still troubleshooting I need help if someone has a suggestion where the problem in the electric circuit of my TB20 could be targeted?
After engine overhaul I have an annoying alternator problem and the fuel gauge was completely errant, made me enforcing a lookup at a maintenance shop.
The alternator was OK on the bench and not opend for warranty reasons therefore. While the fuel indicator is working correctly now (no idea why), the alternator lamp is illuminating intermittently between e.g. 20s to 3, 15 or 20 minutes not charging and unloading the battery. This starts when the charging current commutes at about 2 Amp reading on the gauge.
“Resetting” the Alternator field switch ever after the Alternator light is illuminating after seconds or minutes it helps for seconds up to severel minutes and the Alternator powersupply is indicating correct voltage (28.1 – 28.2 V) and loading from -10 Amps commuting down to -1, -2 Amp.
Would be very pleased if you have any idea where to lookup.
Regards,
Chris
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…
This is a schematic I have found from the POH
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?
I would look for a common ground connection. A corroded ground can cause intermittent indications.
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.
Txs, OK – going to inspect that. 
