There I was, flying along, minding my own business, and I get an "EIS VOLTS" warning. Uh oh, losing an alternator.
Pulled the cowl when I got home. Internally regulated Plane Power, so basic diagnosis is simple. If you have bus voltage at the B lead, and bus voltage at the red wire, the problem is internal to the alternator. I had good volts, so off it came.
Quick inspection inside the back cover didn't turn up anything obvious. Pulled the regulator/brush assembly. Brushes look good, commutator is smooth, about 3 ohms through the rotor (field) windings, no short to ground. Hmmm. pull the rectifier screws, stand up the stator connections, and they check good too. Ok, doesn't leave much, so I get a new IC regulator from a buddy and installed it. Back on the airplane it goes....and doesn't charge. Whatttt?
Recheck field power, and the B lead, and make sure it's not an indication problem by cycling the EFIS from main buss to backup battery. All good. Out of time, got a business trip in the AM, so I buy a new, identical 60 amp Plane Power (Hartzell Engine Technologies is right here in Montgomery). I'll get the old one shop-checked and overhauled as necessary, then I'll have a spare.
Out to the airport, bolt on the new alternator, do a run-up....and it doesn't charge either.
Finally I go into Old Car Guy mode. Forehead slap; I've seen this before, and besides, there isn't much left. I walk around to the front, pull out the three prong field/indicator plug, and look real close with a 10X magnifier. Nope, hadn't missed a burned socket, and they all looked clean, but just the same, I squeezed the sockets closed just a bit, and plugged it back in.
Yep, that was it; a runup said I was now blessed with many vigorous electrons.
Problem appears to be unsupported wire where it exits the back of the plug. The little square sockets in the plug are not held tightly by the plug body, so the socket and wire can vibrate around. Eventually wear/debris/corrosion/loss or spring pressure makes the connection(s) intermittent or non-conductive.
Pulled the cowl when I got home. Internally regulated Plane Power, so basic diagnosis is simple. If you have bus voltage at the B lead, and bus voltage at the red wire, the problem is internal to the alternator. I had good volts, so off it came.
Quick inspection inside the back cover didn't turn up anything obvious. Pulled the regulator/brush assembly. Brushes look good, commutator is smooth, about 3 ohms through the rotor (field) windings, no short to ground. Hmmm. pull the rectifier screws, stand up the stator connections, and they check good too. Ok, doesn't leave much, so I get a new IC regulator from a buddy and installed it. Back on the airplane it goes....and doesn't charge. Whatttt?
Recheck field power, and the B lead, and make sure it's not an indication problem by cycling the EFIS from main buss to backup battery. All good. Out of time, got a business trip in the AM, so I buy a new, identical 60 amp Plane Power (Hartzell Engine Technologies is right here in Montgomery). I'll get the old one shop-checked and overhauled as necessary, then I'll have a spare.
Out to the airport, bolt on the new alternator, do a run-up....and it doesn't charge either.
Finally I go into Old Car Guy mode. Forehead slap; I've seen this before, and besides, there isn't much left. I walk around to the front, pull out the three prong field/indicator plug, and look real close with a 10X magnifier. Nope, hadn't missed a burned socket, and they all looked clean, but just the same, I squeezed the sockets closed just a bit, and plugged it back in.
Yep, that was it; a runup said I was now blessed with many vigorous electrons.
Problem appears to be unsupported wire where it exits the back of the plug. The little square sockets in the plug are not held tightly by the plug body, so the socket and wire can vibrate around. Eventually wear/debris/corrosion/loss or spring pressure makes the connection(s) intermittent or non-conductive.
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