RH mag stopped working all of a sudden

[toomany]

we were holding for departure for a 6 hr flight to hotsprings sd when i went through the preflight run up etc. On mag check the RH mag failed completely, not even a sputter out of it - which was strange bc i checked the mags during taxi at low rpm like i normally do just to see if they are throwing sparks, and they were fine.  We notified the tower of the mag issue and taxied back to do a little looking.  I suspected the key switch as the culprit but when we did continuity to the p-leads in the rh, lh and off positions everything checked out.  We then disconnected the p-leads on the rh mag and did a run up - everything was smooth on the rh mag. We then took a look at the p-lead on the rh mag and noticed a little bit of shielding sticking out of the connector - we removed the connector and installed a new one and reconnected the p lead.  During the run up everything was as it should be so we put the cowl back on and went to sd.  

during the flight we were discussing the mornings events and it was recalled that when we were doing the continuity check on the switch that there were a few times that we got intermittent ohms readings which was thought to be when the meter lead was touching the p-lead and the piece of shielding sticking out of the connector - it was determined the shielding for the p lead was grounding out on a braided plug wire.  

i had the mag rebuilt last week just to eliminate any potential issues which may have been intermittent and not addressed. 

[N201MKTurbo]

All of these things could be correct. When checking these things you need to bend them every which way and make sure they work in all positions. It usually isn’t the shield, but the insulation on the P lead wire itself that is the problem, but when you redo it, you usually cut off the cooked and cracked and brittle insulation on the wire itself. Which fixes the problem.

[carusoam]

Great pirep toom!

Nice way to handle the problem.

Thanks for sharing the details…

Should I invite @Rmag for a comment???  

Best regards,

-a-

[Fly Boomer]

6 hours ago, toomany said:

during the flight we were discussing the mornings events and it was recalled that when we were doing the continuity check on the switch that there were a few times that we got intermittent ohms readings which was thought to be when the meter lead was touching the p-lead and the piece of shielding sticking out of the connector - it was determined the shielding for the p lead was grounding out on a braided plug wire.  

These things are never easy.  Nice bit of sleuthing!

[LANCECASPER]

11 hours ago, toomany said:

it was determined the shielding for the p lead was grounding out on a braided plug wire.  

In 2015 I bought a TLS that had never been converted to a Bravo. An early upgrade that I did which made a noticeable difference in how smoothly it ran, before doing the Bravo upgrade in 2018, was replacing the original braided ignition harness with a new silicone ignition harness along with Tempest fine wire plugs. When leaned out, I could get it to idle down around 600-650 rpm while taxiing, without stumbling, after changing those items.

[toomany]

we're probably putting silicon wires on it at anual in may and putting the fine wires back in.  we had the regular "football" plugs installed from the engine shop at rebuild 150hrs ago.  i had the fine wires in shortly after rebuild because they're low time but had a pretty noticeable miss during run up so i just put the regular plugs  back in. does anybody have a good way of testing out fine wire plugs?  Also, what's the best way to clean them?

[LANCECASPER]

36 minutes ago, toomany said:

does anybody have a good way of testing out fine wire plugs?  Also, what's the best way to clean them?

I've tested the ohms before, but on the Tempest they always stayed low. 

Mine burned very clean, I've sprayed carb cleaner on them just to clean the electrode and the threads.

[carusoam]

The only known issue for Tempest fine wires, a couple of years ago…

was the center electrode would get away…

Tempest changed procedures, solved that issue…

Best regards,

-a-