Mag or ignition switch troubles, KVNY

[TStepp]

I’m AOG Van Nuys this week and could use some advice:

1. Recommendations for trustworthy A&P mech on / near field.

2.  Troubleshooting tips.

After routine run up including mag check takeoff normal until ~2k’ AGL noticed tach red light indicating left mag failure. There was No noticeable sound or drop in performance. Checked ignition switch set to Both. Pressed tach buttons to confirm mode selection was correct.  Switched ignition to L, R, Both, and Off - no difference. Returned to base and Landed uneventfully. Ignition switch made no difference shut down normally by mixture shutoff.  Now AoG 100 miles from home. 

This should be easy, no?  Thanks in advance for tips. 

TStepp

’67F 

[RLCarter]

If I read this correctly, the light is the only indication of a failure? No loss of power, no mag drop when checked?

[Hank]

If there was no loss of power running on either magneto alone, or in the Both position, I'd have kept going. When my left magneto died in flight, with no warning light, I had funny EGT values, and switching the ignition to Left caused the engine to stop. Really got my wife's attention, cruising at 9500 msl, too [not sure if it was the sudden silence or the strong down pitch]. Both made it restart, and I continued on Right, releaning.

Cranking the engine is a challenge with a dead left magneto, also, since the right mag is grounded out in the Start position. Mine turned over rapidly with no fire, but when I released the key, the now-powered-up Right magneto made it catch.

Edited June 11, 2018 by Hank

[MB65E]

Well you happened to be AOG at the the best place in the world to be AOG. 

There is an accessory shop near by, I know of a few shops that might help. 

Ray at Stealth Aviation is located on the NW corner in the prop park. He’ll be able to help!

PM me if your need more info. 

-Matt

[TStepp]

Thanks guys. Ignition switch position changes made no difference whatsoever. Couldn’t even shut it off.

Maybe a switch or p lead problem.

Couldn’t tell for certain whether I was running one or two mags, as switch position was inconsequential.

Without knowing I had 2 good mags, return to VNY vs overflight of LAX and Pacific ocean with few landing options seemed most prudent. Home base is 100 nm south at KCRQ. 

[RLCarter]

11 minutes ago, TStepp said:

Thanks guys. Ignition switch position changes made no difference whatsoever. Couldn’t even shut it off.

Maybe a switch or p lead problem.

Couldn’t tell for certain whether I was running one or two mags, as switch position was inconsequential.

Without knowing I had 2 good mags, return to VNY vs overflight of LAX and Pacific ocean with few landing options seemed most prudent. Home base is 100 nm south at KCRQ. 

wise choice, always better to be on the ground with an unknown issue..... sounds like it might be switch time, unless both "P" leads are open

[Guest tommy123]

Check p lead continuity

[Guest]

I would be highly unlikely that both P leads failed, the ground from the switch is common to both P lead circuits.  A bit of checking with an Ohm meter is in order.

Clarence

[Jim Peace]

Two trustworthy guys:

Lance Yomtob 661-305-9200 he practically rebuilt my Mooney

Matt Jackson, his company is Classic Airworks,  I don't have his number

He just moved into a new hangar at the prop park, near Lance,,,everyone is friends...Lance may have his number....

[carusoam]

TS,

Do you have access to your logs?

There aren’t a lot of ignition switch failures to point to.  There has been one or two that I can think of...

If the switch doesn’t do anything... when turned... sounds like a pretty good place to start.

Do a search on the ignition switch... It will have a couple of pics and wiring diagrams and a discussion on how it works...

Best regards,

-a-

[1964-M20E]

I agree with DOC the ground wire from the ignition switch maybe you issue especially since you cannot shut it down with the ignition switch.  Which also means you have hot mags so be careful when rotation the engine by the prop.  This would make starting harder and kickback a possibility since you are not grounding the right mag and the normal points on the left mag. i.e not using the retard points when starting and trying to stat at 25 degrees BTC timing.

 

 

[N201MKTurbo]

If I recall, your P Leads go through a big Cannon plug. Make sure the plug is tight.

[TStepp]

Thanks everyone - Bill Noctor at Mather is looking it over and will advise. Agree it sounds like the switch or associated wiring.  T

[jamesm]

Don't know if this helps ... yeah evreybody has their favorite search engine and web sites

http://www.aircraftmagnetoservice.net/magneto-troubleshooting-guide

 

James '67c