What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

p-Mag inop on mag check

werxcv01

Well Known Member
RV-8, Lycoming O-360, one Slick magneto, one P-Mag model 113. New plugs on both 6 months and 26 hours ago. Auto plugs are the solid terminal ones. Today on run up, the engine lost all power when switching to R for the P-Mags. The aircraft has an Off\Right\Left\Both\Start switch with a separate toggle switch to remove ship power from the P-Mag to check the internal alternator. At the hangar, the LED on the P-Mag was red with the master on then dark with the ignition switch on. The P-Mag was last serviced at the factory 3/2017 - rebuilt, recalibrated, and Q.C.’d. I am not the builder. A reading through the installation manual did not help. Any thoughts would be appreciated.
 
... A reading through the installation manual did not help. Any thoughts would be appreciated.
I'd get your ohm-meter out there and see if you have the right connections to the green connectors on the pmag.

This is from Page 26 on the manual I have:

pmag wiring from manual page 26.png

The Troubleshooting guide seems to show that the LEDs are indicating all is ok based on what you wrote. Perhaps confirm with a helper that you get the light burst when you power it on. My money's on a wiring issue, perhaps with the key switch.
 
Thanks. The airplane has a few hundred hours with the current set up so I believe the wiring would be correct but the suggestion about the switch may be helpful. A couple of times the master has not powered on the first time I flipped it. Probably need to check the master, key switch, and P-Mag wiring.
 
Thanks. The airplane has a few hundred hours with the current set up so I believe the wiring would be correct but the suggestion about the switch may be helpful. A couple of times the master has not powered on the first time I flipped it. Probably need to check the master, key switch, and P-Mag wiring.
There have been reports of wires that are not properly supported at the pmag end coming loose.

Also, probably a good idea to check the timing. If something bad happened and the timing is way off, it would also look like it's not working when you do the mag check. It's an easy process if you have not done it yet. Take care when moving the prop.
 
Check the connections on the back of the key switch. I had a screw back off of the terminals on the key switch. For me it was the starter. The wiring was tight and I would get intermediate contact between the ring terminal and the switch contact on the back. Found the tiny screw on the floor under the carpet.
 
I note that VAF gets a lot of posts on “ignition switch issues” - especially when going to one or more EIs.

After being stranded with a spam can caused by a finicky ignition switch I decided to never use one in my planes - and have not.

So for you still building (or those getting ready to update your panel) ditch this 1960 Cessna leftover and just use simple toggle switches for ignition and a push start button. This goes for whatever type of ignition you run.

While you are at it, also ditch the stupid split master/alt switch.

Carl
 
Give Brad Dement a call at E-mag. He just helped walk through an install and troubleshooting sequence on P-mag (114- new version). He can tell a lot from what you share with him.
 
Give Brad Dement a call at E-mag. He just helped walk through an install and troubleshooting sequence on P-mag (114- new version). He can tell a lot from what you share with him.

I ended up shipping the mag to E-Mag for an overhaul. The circuit board had to be replaced. They quickly turned the unit around and got it back to me. Check out my “Don’t do this” thread for more details.
 
Back
Top