Electrical Problems

[Hyflyer86]

Hi Guys:

I recently had a local shop change the front alternator on my '73 P337 due to a fault light. When they did the test run, still had the light; the gear doors opened; the OAT/Tach CB popped; the warning horn was sounding. I took it back to the garage. I am an A&P but never worked on a 337. I just bought it a month ago.

First the gear doors; scary. I couldn't find a faulty wire or circuit in the front engine compartment or NLG well. I went to the wiring diagram and looked for logic that would allow the power pack to start and the door to open. I disconnected the #4 terminal block wires in the NLG well. That did it. I suspected a shorted diode in the circuit but I could not find the diode. Anybody??

I pulled the dual warning and over voltage sense boxes. Warning box looks good. Over voltage box had shorted diode and burned trace. I replaced/fixed those. I re-installed both but did not power system up yet. I suspect that will fix the alternator light. The warning horn is real and I suspect that a gear switch is tripped.

Back to the electrical schematics to look for the popped CB on the OAT/Tach lines. I know the mechanic removed the mags to get the alternator out. I think that he may have connected the mag tach wire to the alternator instead of the tach points? I have not been able to ascertain that connection at this time. I am open to suggestions where to look for that gremlin.

Bill N86C
Hyflyer86