Originally Posted by
The Heff
I remember being told during my own flying training (albeit on a Cessna 150) that if the 'Low Voltage' warning light remained lit, then the engine should immediately be shut down. I've not looked at a Piper checklist for sometime, but I believe that this is the same. Can shutting down the engine immediately after start cause damage to the engine, and how?
One cause of the low volt light being on could be that the starter bendix has not disengaged after the engine started. In other words the starter motor is still trying to turn the prop. This will cause a massive draw of power and result in the low voltage light staying on. This situation can be verified by looking at the ammeter. If the starter is still engaged and the engine is running the ammeter will be pegged at + 60 amps as the charging system tries to keep up with the massive draw of power. Damage to the starter and electrical system will occur quickly so it is important that the engine be immediately shut down.
A more likely reason for the low volt light to be on is that the charging system is not charging. This can be verified by the ammeter showing a slight discharge. An increase in RPM should be tried to see if the situation changes, but most probably there is a fault in the alternator or voltage regulator. You will not be going anywhere with no charging system so you will have to shut down and snag the aircraft but there is no hurry for the shutdown.
I am disappointed that your instructor did not explain all this during your training