09 Jun 2025, 17:42 [ UTC - 5; DST ]
|
|
Page 1 of 1
|
[ 14 posts ] |
|
Username Protected
|
Post subject: Re: c172 starter engaging with master switch Posted: 02 Jan 2016, 17:28 |
|
 |

|
|
 |
Joined: 01/19/10 Posts: 1884 Post Likes: +747 Location: Canberra Australia
Aircraft: V35
|
|
I have no knowledge of the wiring of a C172, so all of this is entirely at your risk.
It might be worth removing the cowls and tracking the wire/s out of the starter motor. If there is a thin wire and a fat wire into the starter motor, see if the thin wire goes to a relay that's separate from the starter - it may be that that relay is stuck in. If there's just a fat wire, see if that fat wire goes to a relay that's separate from the starter - it may be that that relay is stuck in.
If it were me and it was an emergency, I'd give any relay that's connected to a wire that goes to the starter motor a good tap with a calibrated tapometer. If there is a thin wire and a fat wire going to the starter motor, I'd give the starter motor a good tap as well - on the bit to which the thin wire is connected. I'd guess the solenoid was in that area.
CAUTION: If I did this, I would triple check that the master/battery switch/es are OFF, and make sure everyone's well clear of the prop when I tested the success of my tapping by turning the master/battery switch/es on while at the controls and on the brakes.
CAUTION: If my tapping was successful and the starter did not engage when I turned the master/battery switch/es on, I would watch the ammeter and other electrical system indications VERY closely after start, to confirm that the starter motor disengaged after start. If the starter motor did not disengage after start, I'd shut down immediately and apply AMUs to the problem.
I reiterate: I have no knowledge of the wiring of a C172, so all of this is entirely at your risk.
|
|
Top |
|
Username Protected
|
Post subject: Re: c172 starter engaging with master switch Posted: 02 Jan 2016, 19:41 |
|
 |

|
|
Joined: 01/06/09 Posts: 461 Post Likes: +161
Aircraft: A185F
|
|
My experience is with a C 185, I suspect they are the same. The key switch (when engaged) powers a single conductor that goes to the solenoid. When this wire is powered the starter solenoid on the fire wall is engaged. The solenoid is about $150-200. If you disconnect the wire at the solenoid and its powered (with the key off) then the problem is with the key switch it the wire, if it's not powered then the problem is the solenoid.
Andy
Last edited on 03 Jan 2016, 11:27, edited 1 time in total.
|
|
Top |
|
Username Protected
|
Post subject: Re: c172 starter engaging with master switch Posted: 02 Jan 2016, 19:45 |
|
 |

|

|
 |
Joined: 07/22/14 Posts: 10053 Post Likes: +20041 Company: Mountain Airframe LLC Location: Mena, Arkansas
|
|
Username Protected wrote: There is nothing that would tell me that after it started the same condition might not exist? If it stayed stuck after start:
You would not hear it. You may or may not have a high current draw on the ammeter You will, eventually, fry the starter, alternator, battery... in no particular order
I'd not fly it.
Just sayin... What Mike said. Do not take chances on this. To many things can go south in a hurry. Now, if I were stranded in an unfriendly place and the natives were doing their best to spoil my party, I would disconnect the leads at the starter and secure them with duct tape......(everybody has duct tape), and then hand prop the little Lycoming and be on my way to the nearest safe haven.
_________________ If a diligent man puts his energy into the exclusive effort, a molehill can be made into a mountain
|
|
Top |
|
Username Protected
|
Post subject: Re: c172 starter engaging with master switch Posted: 02 Jan 2016, 20:29 |
|
 |

|
|
Joined: 05/04/11 Posts: 501 Post Likes: +116 Location: Covington, GA
Aircraft: 421C, 58
|
|
Sounds like a stuck starter solenoid/contactor. Easy to troubleshoot, solenoid should be forward of the firewall. Battery might be as well depending on year. A generic solenoid could be picked up from auto store to make it home. Could be the ignition switch as well...
|
|
Top |
|
Username Protected
|
Post subject: Re: c172 starter engaging with master switch Posted: 02 Jan 2016, 20:45 |
|
 |

|

|
 |
Joined: 07/22/14 Posts: 10053 Post Likes: +20041 Company: Mountain Airframe LLC Location: Mena, Arkansas
|
|
Username Protected wrote: Not sure how it's possible to fry a whole bunch of electrical components without any prior abnormal indications in the cockpit after start, but as I say I don't know anything about the circuitry on a C172.
In any event, Del's suggestion seems to me to be a potentially safer solution in an emergency, provided that:
- the people involved know how to do a safe hand start, and
- it's certain the starter motor is not permanently mechanically engaged. You are right Clinton. I should have placed more emphasis on safety. Thanks for your post. This condition can be very dangerous for the OP and for bystanders. Please be mindful and careful. If you are not mechanically inclined, please seek out someone who is.
_________________ If a diligent man puts his energy into the exclusive effort, a molehill can be made into a mountain
|
|
Top |
|
Username Protected
|
Post subject: Re: c172 starter engaging with master switch Posted: 02 Jan 2016, 21:12 |
|
 |

|
|
 |
Joined: 01/19/10 Posts: 1884 Post Likes: +747 Location: Canberra Australia
Aircraft: V35
|
|
No - thanks for your post.  It highlighted an option that I had not considered for this problem but would now consider in an emergency. (I have hand started an A36 with a 520! The scary bit - which should have been unsurprising - was the ease with which the engine sprang to life.  )
|
|
Top |
|
Username Protected
|
Post subject: Re: c172 starter engaging with master switch Posted: 03 Jan 2016, 00:31 |
|
 |

|
|
 |
Joined: 05/08/10 Posts: 5133 Post Likes: +626 Company: flying rescue dogs Location: midwest
Aircraft: A36
|
|
Username Protected wrote: No - thanks for your post.  It highlighted an option that I had not considered for this problem but would now consider in an emergency. (I have hand started an A36 with a 520! The scary bit - which should have been unsurprising - was the ease with which the engine sprang to life.  ) i hope it was a 2 blade prop 
_________________ blue side up
|
|
Top |
|
Username Protected
|
Post subject: Re: c172 starter engaging with master switch Posted: 03 Jan 2016, 04:58 |
|
 |

|
|
Joined: 02/16/11 Posts: 127 Post Likes: +12 Location: St Louis, Mo (KSET)
Aircraft: 23
|
|
It is the start solenoid or the key switch. If its the key switch disconnecting the small wire from the solenoid will stop it from engaging the starter. if its the solenoid they are rather inexpensive item. Just make sure when you buy a solenoid it is a starter solenoid and not a master solenoid. In a lot of planes they look interchangeable. Also if the engine is equipped with the shower of sparks system just pulling the prop thru will most likely not start it. I think you may get it energized if you have the key on start when pulling the prop thru. Good luck and be careful whatever you do.
|
|
Top |
|
Username Protected
|
Post subject: Re: c172 starter engaging with master switch Posted: 03 Jan 2016, 12:11 |
|
 |

|
|
 |
Joined: 08/13/09 Posts: 9448 Post Likes: +7289 Company: AVSTAR Aircraft of Washington Location: Puyallup, WA
Aircraft: Beech 1079, S/N EB-3
|
|
Username Protected wrote: Not sure how it's possible to fry a whole bunch of electrical components without any prior abnormal indications in the cockpit after start, but as I say I don't know anything about the circuitry on a C172... Doesn't matter if its a 172 or a Bonanza. A starter has high current draw. There is a warning to not have some starters engaged for more than 10 seconds, some as long as 30, before they could get hot enough to damage them. If the starter is engaged while the alternator is working, the current the starter consumes can potentially over heat the alternator from excessive output. If you have a load meter for monitoring alternator current, you will note the high draw, but typical ammeter installation won't necessarily show it. Battery will be drained because the alternator can't keep up with the current draw. About a week ago, had the solenoid stick on an S35 I was doing a dynamic balance on... everything shut off in the cabin, and the starter keeps on a spinning. One needs to act fast in disconnecting the battery. Another bright idea from Wichita - not run starter current through the master switch...!
_________________ AVSTAR Aircraft of WA, Inc
avstarair.com
bonanza.org
Aircraft Maintenance: It is a Team Sport
|
|
Top |
|
|
Page 1 of 1
|
[ 14 posts ] |
|
|
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot post attachments in this forum
|
Terms of Service | Forum FAQ | Contact Us
BeechTalk, LLC is the quintessential Beechcraft Owners & Pilots Group providing a
forum for the discussion of technical, practical, and entertaining issues relating to all Beech aircraft. These include
the Bonanza (both V-tail and straight-tail models), Baron, Debonair, Duke, Twin Bonanza, King Air, Sierra, Skipper, Sport, Sundowner,
Musketeer, Travel Air, Starship, Queen Air, BeechJet, and Premier lines of airplanes, turboprops, and turbojets.
BeechTalk, LLC is not affiliated or endorsed by the Beechcraft Corporation, its subsidiaries, or affiliates.
Beechcraft™, King Air™, and Travel Air™ are the registered trademarks of the Beechcraft Corporation.
Copyright© BeechTalk, LLC 2007-2025
|
|
|
|