Shawn26

Absolutely! A little luck is all I need.

Besides becoming increasingly expensive due to labor and diagnostics, there has been no update. We removed the new 500-hour magneto, sent it to the shop, and they replaced the bearing and contacts components that had already been serviced at 500 hours. We then reinstalled it on the airplane, but there was no change, RPM still erratic. We replaced the entire P-lead wires, but still, no change. The next step is to rebuild a new magneto and install it. I’ve come across a few others on social media with the same issue with the dual mag. This situation is becoming really frustrating, as I've been grounded for about three months. Let me know if you want any further refinements!

I sent you DM. Wondering if you can contact me. Thank you

No, the Mooney it’s not turbo charge. I’ve IO-360.

I believe your engine information EIS works the same exact way as my setup. You don’t have a separate sensor for tac / RPM and the P-lead is the only source of information for your dual mag. You may come across of the same issue I’ve encounter. i just hope Garmin can figure out the problem and provide alternative solution really soon.

I don’t know the UMA part number, but they have one for D-3000 magneto for none certified aircraft. UMA tech-support mentioned they are lots of people using it on certified aircraft, he didn’t know how. Obviously Garmin is not supporting it or provide any guidance on installation. I dropped off the airplane at my Avionic shop. If I get any update on the progress I’ll repost about it. I’m down two months. obviously, I’m not happy about it. We just have to see whats causing this interfering. I’m sure Garmin knows about this issue as I’m not the only one!

My setup was working fine till the mag was removed for 500hrs inspection. I did everything you done! No changes. Unfortunately with D-3000, P-lead is the only source for getting TAC and RPM. I wish UMA would have made RPM sensor for the dual mag for certified aircraft. JPI makes one, and it’s the most reliable and precise way to get the information from the magneto. UMA have one for none certified aircraft for D-3000. I spoke to their technician and I was told many shop install them on certified aircraft but that’s not the route I like to take. I guess we have to stick to the P-lead for now and figure out what needs to be done! My shop suggested to change to new GEA24 version as advised by Garmin. I doubt that solve the problem! Please update if you come across of new information. Thank you.

I came a cross Continental service bulletin for the bendix d-3000 ( SB651 ) I got to look in to it.

If you figure it out, please keep me informed.

You’re correct! lol Mag could possibly be the issue and I was thinking to send it to another place to verify. My mechanic thinks otherwise. Since everything works, engine starts and run normal, he doesn’t think that’s the case.

Yes, there is a ground straps that goes between the engine and the firewall. I finally heard from the Avionic shop, he spoke to Garmin and said they believe there is a interfere or some sort of distortion going on, rather than chasing what is causing it since I did most of the troubleshooting ( beside of checking if the 400ohm resistor gone bad or something in that nature) we should rewire the RPM with a sensor. I hope they are talking about the same sensor. I’ve to double check with them again, I hope this would solve my problem. The airplane has been down for about a month I will definitely look him up on Google and contact him. It would be good to know. Thank you kindly, you’re very knowledgeable. You also helped me to find my #3 CHT issue with the baffle, thank you for that as well.

I checked both P-lead, Center conductor, and the shielding for continuity. No issue there. The shielding is directly to the back of the mag, and the mag housing to the engine airframe is the only source of ground. I checked this triple time, I have solid ground contact when I check it to the aircraft body and engine. I do not see any other spot for ground or see any heavy braided ground strap getting attached to the mag. I don’t recall ever seeing one. I don’t know if I need to reinforce the ground contact between the magneto and the airframe or not really. I came across of this post. The arrow marking ( attached ) I don’t have. http://mechanicsupport.blogspot.com/2010/02/how-to-properly-ground-dual-magneto.html?m=1 I installed both old capacitor. I’d the magneto shop to check them and I kept them for reserve. I thought maybe the new one maybe out of parameter. The result is still the same. There is a distortion when RPM reaches around 1600. I never check under my panel for the connection of GEA24 and the 400ohm resistor to the ignition switch because I didn’t touch anything. And to be honest I don’t know what to look for if I want to inspect it and check the resistor if it may gone bad. I think they make RPM sensor for the bendix dual mag. D3000. I think this is it. https://www.enhancedaero.com/parts/p/rpm-sensor-for-bendix-dual-mag?srsltid=AfmBOoqDYhwv725m9h0R5eoMJoO9bTZHuW-cpYeQRDREPwmotyilzWHS

Thank you. I’ve GEA24. I don’t know what to look for when I’m under the panel. Should I find a shop to do it for me? I don’t want to mess up something.

Yes, the P-lead is connected correctly, and the shielding is grounded to the body of the mag. There is no issue with the grounding, I’ve checked the P-lead wire and the shielding for continuity. Mag is also grounded to the engine. There is no issue there. Engine shuts down when I turn the switch ( mag ) off. the capacitor is connected to the backplate of the mag. Garmin install manual recall for 400 ohm resistor. I don’t know how to look for it or check the connection to the GEA 24. prior to my 500 hours inspection, everything was working fine, I don’t know what went wrong! would you think it’s better to install a RPM sensor ( attached to the mag ) or diagnosed the problem? I was told RPM sensor is a better and accurate installation than a P-lead. I think I should find a shop so they can rewire the installation, hopefully this should do it.

Recently, I removed my Bendix D3000 dual magneto for a 500 hour inspection. During the process, the gears were replaced, and I purchased two new capacitors (KA10-400574). After reinstalling the magneto, I noticed that whenever I exceed approximately 1600 RPM—whether on the Left, Right, or Both magnetos—the RPM reading becomes erratic. Despite this, the engine shows no issues with timing or starting, and it runs perfectly fine even with the erratic RPM readings. When performing a mag check around 1500 RPM, everything appears normal. My Garmin G3X with EIS reads the RPM through the magneto P-leads. I don’t have a separate sensor on the magneto or a mechanical RPM sensor. Initially, I suspected the issue might be related to a grounding connection. However, after checking continuity, I confirmed the magneto is grounded, and all connections appear correct. To troubleshoot further, I reverted to the old, functional capacitor and even pulled the alternator fuse to rule out interference from the alternator, but the erratic readings persist. I contacted Garmin support, but they were unable to assist and suggested I reach out to the avionics shop that installed the system. Unfortunately, the shop is also unsure of the cause. The magneto shop assured me the unit was properly bench-tested and functioning correctly, so I don’t believe the issue originates there. I’m wondering if anyone has experienced a similar issue or could help diagnose the problem. The aircraft is currently located at Van Nuys Airport, and since a functioning RPM gauge is mandatory, I can’t fly it to another shop. Obtaining a ferry permit has also proven to be quite difficult. If anyone has insights or is available to help troubleshoot this issue, I would greatly appreciate it and willing to compensate for their time. I've also uploaded a video of the issue on YouTube for reference. Thank you! https://youtube.com/shorts/umHdKcL2wxQ?si=nLp6FBlf1nmhfDjC