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Topic-icon Starter Solenoid locks up after hard landing

  • Steve Jordan
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1 week 5 days ago #1837

After a hard landing a month ago, the starter solenoid apparently would not close when energized. A mechanic removed, cleaned, and reinstalled the starter cable, but said it looked OK. After he messed with it, the solenoid began to pick-up and start the plane. I replaced the starter solenoid with a new one and even replaced the battery with a new one. Last weekend, after another hard landing, the new solenoid failed to close when energized. I tapped on it with the handle of a pair of side cutter pliers and it began to work again. I have owned the plane for 7 years and this is the first time I have seen this happen. I asked Sky-Tec about the horizontal mounting of the solenoid and they said it shouldn't matter and that Piper installed it that way. Has anyone seen this on their aircraft? Any suggestions?

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3 days 21 hours ago #1846

Hi Steve,
Interesting problem. I suspect it has more to do with loose connections than with the internal parts of the solenoid hanging up. The piston in the solenoid is held open by a spring. When power is applied through the coil of the solenoid (the small wire) current flow through thousands of windings creates an electromagnetic field that overcomes the spring, causing the piston and internal movable contacts to move into contact with the internal large wire terminals.
The most common problem with solenoids, also called contactors is erosion of the internal contacts which creates high resistance through the solenoid and in extreme cases, causes the solenoid to weld itself shut.
So I would look closely at the wires on the starter switch or "mag" switch in the panel, and the small wire connections on the solenoid itself. Tell-tale signs of bad contact are discolored wire insulation, and erosion of the ring on the wire terminal.
I would also take a good look at the wire connection on the starter motor.
Make sure the small wires to the solenoid are in good shape and I think you'll find that your starter problems will be solved.
Happy Flying.

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