1968 172I with 180 hp avcon conversion. Had a strange event last week
where the alternator circuit breaker (70 amp) popped. Was with an instructor and he reset it. A few minutes later it popped again. Turned off nav lights etc and a few minutes later it popped again. It done it a total of about 4 times. No other problems were noted and now we cannot duplicate the problem on the ground. Voltage regulator was replaced about 30 hours ago. At that time it had full fielded the alternator and fried the battery. no problems since, until this happened. Any ideas?
Thanks, Larry Melton Claremore oklahoma
I would first check the connections at the alternator, to make sure that the baffling is not grounding out A+, There should be a protective boot over this connection. If no defects found, I would suspect the Alternator brushes, or an internal problem such as rear needle bearing going away allowing the rotor to run off center thus internally grounding the stator.
bACK INTO THE FLYING SEASON AGAIN. OVER THE WINTER, THE ALTERNATOR WAS REPLACED AND WIRING CHECKED. LO AND BEHOLD WENT FLYING THE OTHER DAY AND NOTICED THE RADIOS FLICKERING AND GOING DEAD. THE BREAKER HAS POPPED AGAIN. BATTERY HAS BEEN CHECKED AGAIN AND DOESNT SHOW ANY PROBLEMS. THIS IS MAKING ME NUTS. LARRY MELTON
Larry, I would give the wiring a good shake down again. Sounds like a direct short, either on the A+ or Alt field wiring. A short on the main buss bar could also be a problem. The intermittent nature is probably due to vibration. I would assume with the 180 H.P. conversion that most of your alternator wiring is new, which makes it more puzzling. Good luck.
Try checking the battery relay. We had a similar problem on a P210, and the battery relay was going bad, not allowing the battery to charge much, and over amping the alt and causing the radios to flicker. Might be something to look into.
It's been my experience that once a 'higher amperage' breaker pops, it is weakened, and in the future will pop at lesser then designed loads. There's a newer p/n breaker out there for the single engine cessnas, tho I don't have the number here at home.
