Power Wagon [886] Ambulance wiring question !!

Yea pull it and get it tested I am sure you will find that 1 of the 3 phases in the stator is fried or the diodes are toast. With these issues it will charge good enough to keep it running but not enough to keep the battery properly charged. The flickering lights is a clue that 1 phase is not working. Your local Autozone can test it.