Although my 750 flies very well (I have 50+ hours on it), I continue to
           have problems with my MGL panel. I have talked to both Matt at MGL and Wayne
at composite designs (LSA power panel) multiple times without success
in solving the problem. The bottom line is that my MGL radio (V6) and
Discovery lite EFIS  work fine while my engine (Jabiru 3300) is off. Once I start the
engine, the AHRS part of the EFIS quickly freezes, and my radio stops
working. The intercom works, the numbers stay on the face, but I don't
receive or transit. Sometimes, keying the mike ( PTT button) will start it
working, but at best it's intermittent. If I recycle the EFIS power, the
EFIS will work for a while, then freezes again. Just the AHRS part. The
engine monitoring stuff from the RDAC has always worked fine. I traded out
the EFIS once to no avail. I put a capacitor across the power supply (as
suggested by both Matt and Wayne) to no avail. My first flight was 6 January 
            and other than my test area, I haven't ventured very far without a
           reliable radio and EFIS (I have steam gauge ASI, altimeter, skid ball and compass
as well as a garmin 496 so I've never been or felt unsafe). Even though I
            have about 8k in the MGL system (EFIS, radio, transponder and ADS-B), after 10
months, I'm about ready to throw in the towel and put in another system.
I've had an avionics guy working on it for several months now, redoing
grounds, checking coax and shielded wires, etc.  He is as befuddled as me.
           I can't help but think the Jabiru has something to do with this, and perhaps
specifically the voltage regulator (which I got a new one and changed as
well). My voltage regulator is wired as prescribed by Wayne for the Jab 3300. Anyone have any thoughts or ideas on this?  Thanks.

Views: 880

Reply to This

Replies to This Discussion

Maybe its the engine but I think you have an electrical/grounding issue.  I would suggest signing onto and signing up for the aeroelectrics email forum and post the issue there.  Some very knowledgeable folks there... here's a link:

Do you have ALL grounds connected to a "forrest of tabs" panel?

Do you have any RF cable running right alongside a data cable?

I tend to agree it is probably a grounding or connection issue. When the engine is off, no vibration, engine on. vibration causes your problem. This would seem to indicate a bad ground issue or loose connection. The only other thing may be some sort of interference from the alternator but you can test that theory by disconnecting it from the system and running the engine with the instruments running either off a ground source or just the battery and see if it still happens. Since it seems to be something with ADHRS I might check that wiring first and also check for a power line running next to or near the ADHRS or it's data line causing electromagnetic interference..

I actually did that (ran the radio and EFIS) directly off of the battery and disconnected the voltage regulator (and hence the power coming from the engine) with the engine running with the same results My plan is to again go over every ground and connection to the EFIS and radio and look for anything loose or improperly wired.  Vibration seems to be the source.  Perhaps the tenth time will be the charm. Thanks. 

Any luck yet? I'm considering MGL , but this concerns me.

Still trying to figure it out.  Honestly, no one else with an MGL system has ever contacted me with a problem similar to mine.  Matt, at MGL, has been extremely helpful, unfortunately to no avail.  After I sent my Discovery Lite EFIS back to be checked, he sent it back and said it checked out.  After a couple months, he agreed to completely replace the unit.  Same problem.   I has to be something unique to my engine, electrical system setup, however for the life of me, I can't figure it out.  I've had an avionics guy intermittently working on it for the last several months. He's rewired grounds, the jacks, etc.  No joy.  So, I think this is somehow unique to my setup and I'm not sure it's an MGL problem.  For what it's worth.

The wires from your magnetos to your ignition/start switch, and the AC power wires from your engine to the voltage regulator, are each individually separate(not twisted pairs), individually shielded, and the shields grounded at the nearest point to the wire ends?

They aren't twisted pairs, but they aren't shielded either.  Should they be??


Yes they should be.  Shield those wires, begin with the AC power wires from the engine to the external rectifier/regulator, start the engine, see if it makes a difference with your MGL.  Then shield the ignition wires.  Make sure you ground the shield braid. Hang in there, even if this does not solve your problem, keep at it, you will solve it.  

 Over twisting of wires can be problematic. 

 You mentioned you put a capacitor across the power supply. Connect an oscilloscope(DSO) to the same point as capacitor - set tigger for falling edge and record the data points of the failure.  The problem may be caused by voltage going outside the operating parameters of the electronics therefore causing a lock up.  Too high or too low voltage will cause strange problems. 


New from Zenith:

Zenith Planes For Sale 

Classified listing for buying or selling your Zenith building or flying related stuff...

Custom Instrument Panels
for your Zenith

Custom instrument panels are now available directly from Zenith Aircraft Company exclusively for Zenith builders and owners. Pre-cut panel, Dynon and Garmin avionics, and more.

Custom Upholstery Kits for your Zenith Aircraft:

Zenith Vinyl Upholstery Kits

Zenith Apparel from EAA:

Zenair Floats

Flying On Your Own Wings:
A Complete Guide to Understanding Light Airplane Design, by Chris Heintz

Builder & Pilot Supplies:

How to videos from

Developed specifically for Zenith builders (by a builder) these videos on DVD are a great help in building your own kit plane by providing practical hands-on construction information. Visit for the latest DVD titles.

Aircraft Insurance:


West Coast USA:

Pro Builder Assistance:


Transition training:

Golden Eagle Aviation

Pianosa Flying Farm

Aircraft Spruce & Specialty for all your building and pilot supplies!

© 2021   Created by Zenith.Aero.   Powered by

Badges  |  Report an Issue  |  Terms of Service