What are the odds of getting 3 defective magnetos?

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TXBob99

Filing Flight Plan
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TXBob99
Long time lurker and first time poster. I need a little advice from POA if I could.

Short story:
What are the odds of getting 3 defective brand new magnetos from Continental?

Longer version:
I bought a brand new plane with an O200 engine. During one of the first runups I noticed I was not getting an RPM drop on one side and the tachometer reading went to zero on the other side (still ran fine). Turn the switch to 'off' and the engine still ran fine. I thought 'bad connection on p-lead'.

The shop did some troubleshooting and determined the magneto was bad so they coordinated with Continental to get a new one sent out under warranty next day. Fantastic!

New magneto arrives and the shop bench tests it and says it tests the same as bad one. I think they said it was internally grounding or something like that but I'm not 100% sure. I suggested that it would be very unlikely that I get two bad magnetos from the factory and asked that they contact Continental's tech support and talk to them directly just to be sure. Continental apparently agreed with the shop's diagnosis and that the second magneto was bad. They sent a third one under warranty.

The shop just called and the THIRD magneto is also testing bad. They said they talked with Continental many times over the last few weeks and Continental suggested putting the capacitor from the new magneto into the engine's good original magneto. The problem followed the capacitor suggesting there was a problem with the capacitor.

Continental said they might have received a batch of bad capacitors and they are going to try sending a FOURTH magneto.

I'm thinking someone MUST be missing something here but the shop insists that they thought the same thing every time and triple checked all of their work each time and they are following all of the testing procedures exactly as Continental is recommending.

Is this even possible? Aren't these tested at the factory? Any ideas what else could be going on here? Anyone else have similar problems with magnetos?

Any suggestions would be greatly appreciated!
 
Continental makes the former Slick mags, which use a feed-through condenser (capacitor). The case of the condenser screws into the magneto housing, grounding it, and a lead from the inside end of the condenser goes to the points while the outer terminal gets the P-lead. It sounds like the P-lead end is dead, which would be strange for a feed-through construction.

upload_2023-5-17_18-22-20.jpeg

Yellow wire to the points, P-lead to the stud with the nut.

I see a Service Bulletin in process.
 
Continental should be sending a tested good capacitor for your shop to install on the "Defective" magneto. That seems to be the only defect, and the shipping will be cheaper.

And, yes, they could have received a whole box of defective capacitors, and they should be testing all the in stock mags and capacitors, to be sure that the do not ship another defective unit, or assemble another new unit with a defective Capacitor.

Setting up to test capacitors is a pain, but testing the second, third, etc., is quick and easy.
 
I’m a little confused here.

TCM ( Continental) makes the former Bendix mags.

Champion produces Slick products.

The O-200s overwhelmingly use Slick mags.

So what type mags do you actually have?

The Slick capacitor shown has a rather low torque for the P-lead.

Exceeding that will “ pull” the terminal and damage the capacitor.

Some TCM/Conti/Bendix mags have a self grounding feature in the Breaker Compartment.

On those mags you must firmly tighten the p-lead connection or the mag will be internally grounded

and inoperative.

Not all shops and Techs know everything. Most folks are proficient with what they are involved with.

A shop that primarily services kerosene burners may not be as familiar with mags.
 
Thanks for the great replies!

The service bulletin comment gave me an idea to search previous SBs for this issue and, sure enough, continental has issued a couple over the years for this exact issue. Nothing recent but it sounds like that might change soon.

I am a little nervous about who pays for all of the labor though. The previous SBs looked like Continental would cover 1.5 hours of labor and we are waaaaaaay over that now. :/
 
TXBob99 said:
we are waaaaaaay over that now.
Click to expand...
Inquire with Continental on submitting a warranty claim for the labor you've gone through now on the 3 mags/condensers since TCM support is involved and sending you parts. Either check the warranty process online or call the warranty division directly.
 
geezer said:
And, yes, they could have received a whole box of defective capacitors, and they should be testing all the in stock mags and capacitors, to be sure that the do not ship another defective unit, or assemble another new unit with a defective Capacitor.
Setting up to test capacitors is a pain, but testing the second, third, etc., is quick and easy.
Click to expand...
Champion will be inclined to trash the whole batch. If some are open inside, the rest that test OK might have a weak connection that will fail in service, leaving a mag hot after shutdown.

If the failure involves the disconnection of the points lead, the mag stops sparking. That condenser is not just there to stop arcing at the plug; that arcing represents a gradually falling coil current, and the mag needs an abrupt fall to get the secondary's voltage high enough to spark. The condenser absorbs the electron surge when the points initially open, and once the condenser is full, the points are too far apart for the primary current to jump.

In a magneto, that condenser also provides a push to start the next coil charge in the opposite direction. Unlike battery ignition, the mag is an AC device.

One has to wonder if Champion is only testing random mags instead of every single one of them. For something that costs so much, one should be getting a test report with every mag.

Or maybe their test doesn't include the P-lead circuit function. I bet it will now.
 
Since retired Slick Rep Joe Logie said they had a video on every mag they repaired.

Unsure whether manufacturing was the same.
 
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