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Topic-iconStarter Solenoid locks up after hard landing

  • Steve Jordan
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4 months 1 week 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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4 months 3 days 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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2 months 2 weeks ago #1899

Steve,
Thanks for the reply. Just to close the loop, I replaced all of the 50 year old aluminum cables with new #1 AWG copper cables from Bogert Aviation. I also modified the battery box with a mod kit from Bogert Aviation. Skytec (the starter maker) didn't want to discuss troubleshooting the starter till the cables were replaced. This needed to be done, but did not solve the problem. However, when the starter was removed (had only been installed less than 4 years) it was found to be falling apart. The motor had backed off from the gear housing and some internal wiring was loose. The starter was cleaned and repaired and is now working as designed. So I guess you had it right, there was something loose. I just can't imagine why the starter began to fall apart in such a short time. However, I did find out about the Piper SB regarding the dangerous aluminum cables, which I think may have caused my previous battery to fail (case ruptured around the positive terminal).
Steve Jordan

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2 months 2 weeks ago #1900

Hi Steve;
Thanks for the follow up report. I installed the Bogart copper cable kit in my Comanche and believe it's a very worthwhile update.
I'm glad you found your problem. I am surprised the SkyTec starter didn't hold up better. I installed a Lamar starter which has been faultless for the last 7 years.
Glad you're back in the air.
Happy Flying

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2 months 1 week ago #1908

I own a FBO and we have had several Skytec starters that the bolts have worked loose on. SkyTec has replaced each one under warranty. I think the newer starters have been updated to prevent this from happening again. I have also had two SkyTec starters that the bendix has failed on. The starter bendix will energize but will not engage the ring gear.

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2 months 1 week ago #1909

Hi, Thanks for passing on your experience on SkyTec starters. I noticed that Hartzell, that now owns SkyTec has owners manuals and installation and shear pin repair instructions on its website.
I also found quite a few posts on different owners groups sites reporting problems with the "bendix."
Hopefully Hartzell has addressed these problems.

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