Testing a mag

[Glenn.hunt]

How does one go about testing a mag? My top mag appears to be dead. Switches checked out, wiring checked out for continuity and grounding issues. This is really odd because one day it flew great and the next day it was dead.

[robin]

Glenn,
I hope this helps:

I recently had an intermittent magnetron problem. Doing a routine mag check in the air and the engine ran rough on primary ( mags) and also on the ground prior to shut down. However when I came back later to diagnose I could not find a problem. So I flew and did mag check in the air, again running rough on primary. Again could not get the problem on restart on the ground.

All wiring and switch checked ok. Thought it may be a magnet problem and replaced magnet. Cheap. Just as an aside, I have used a wider gap than the shim provided as it was hitting from the first start of the engine. Never had a problem with the mags till now. Not a magnet problem.

Now it had be a magnetron problem. I disconnected both p-leads so both mags are always live and I ran the engine on the ground for about 20 minutes until I got a mag failure. I then connected 1 p-lead, ran the engine and did a mag check with the switch on and then off. With the switch on the engine ran rough, but when I switched that mag off the engine died, so the other mag was causing the problem. Replaced that mag and all good again.

I don't know why the mag failed, perhaps heat, but with only 200 hrs on the engine I was surprised. I know other aerovee owners who have had to replace both mags, so this is definitely a reliability issue. I highly recommend that everyone do a primary / secondary check before takeoff, again in the air at cruise, and again prior to shut down. These failures do not give any warning.

Does anyone know, what is the expected life of a magnetron?

Robin
Sonex 1071

[Glenn.hunt]

Thanks Robin, Mine sounds like the exact same problem as yours. Did you buy the replacement mag from Sonex or did you buy it off the Internet? I think I will buy two and have one on the shelf.

[robin]

Glenn,
Got it from Sonex.
Robin.

[mike.smith]

This is the one I bought, and is currently installed and working:

#33-345 ignition coil.
http://www.amazon.com/Oregon-33-345-Ign ... B0009XHKDS

Doing the P-lead thing one at a time is what I did, too. In my case it was not the mag, but at the time I thought it was. With the p-leads off the engine is "live" so be careful!

Mike Smith