rturbett Posted April 9, 2024 Report Posted April 9, 2024 1980 m20 J The ammeter was fluctuating "wildly", so I cleaned the connectors on the master. It now just mildly twitches, a fraction of what it had done previously. This only shows up in flight, and have tried turning of lights/ strobes etc with no change. It's not consistent, or constant in flight either. the ground on the alternator looked good. I'd like to make this perfect- especially since I have one electric magneto. Any other thoughts before I ask the local shop to start digging? Thanks Rob
Ragsf15e Posted April 9, 2024 Report Posted April 9, 2024 1 hour ago, rturbett said: 1980 m20 J The ammeter was fluctuating "wildly", so I cleaned the connectors on the master. It now just mildly twitches, a fraction of what it had done previously. This only shows up in flight, and have tried turning of lights/ strobes etc with no change. It's not consistent, or constant in flight either. the ground on the alternator looked good. I'd like to make this perfect- especially since I have one electric magneto. Any other thoughts before I ask the local shop to start digging? Thanks Rob If you’re still concerned, possibly pull the field cb in flight and see what the ammeter looks like? That would eliminate the alternator and should give a good idea of your constant amp draw. Depending on what kind of lights you have and if pitot heat is on, you might see -10-15 amps. The electronic mags run a long time on battery power. 2
geoffb Posted April 9, 2024 Report Posted April 9, 2024 clean and tighten the spade connector on the back of the ammeter field switch. Terrible application for a spade terminal. 2
Yetti Posted April 9, 2024 Report Posted April 9, 2024 measure voltage with plane running with digital VOM. Check Grounds to the instrument cluster. Report back.
231LV Posted April 10, 2024 Report Posted April 10, 2024 Hate to be the bearer of bad news but whenever mine started "twitching" or swinging wildly, my coupler was slipping. I have replaced a coupler maybe 3-4 times in my 20 plus years of ownership. My A&P chased down everything else it could possibly be (including everything mentioned in this thread) before pulling the coupler. Now, we just go straight to the coupler and the problem is solved.
PT20J Posted April 10, 2024 Report Posted April 10, 2024 The M20J has a Lycoming. Belt drive alternator - no coupler. 2
rturbett Posted April 10, 2024 Author Report Posted April 10, 2024 Was happy to have a conversation with Sure Fly- The magneto draws lest than an amp per hour off the battery- meaning 10 plus hours of operation should the alternator fail. That takes care of half of my worrying.
LANCECASPER Posted April 10, 2024 Report Posted April 10, 2024 2 hours ago, rturbett said: Was happy to have a conversation with Sure Fly- The magneto draws lest than an amp per hour off the battery- meaning 10 plus hours of operation should the alternator fail. That takes care of half of my worrying. Just make sure you have a good Concorde battery. Friends don't let friends fly with Gills. 1 1
Ethan Posted April 10, 2024 Report Posted April 10, 2024 Could it be the draw on your system of the strobes (LED or Xenon)? My ammeter twitches each time my LED strobes fire. 1
rturbett Posted April 11, 2024 Author Report Posted April 11, 2024 4 hours ago, Ethan said: Could it be the draw on your system of the strobes (LED or Xenon)? My ammeter twitches each time my LED strobes fire. That was my first thought- but still did it when I turned everything off in flight
mike_elliott Posted April 11, 2024 Report Posted April 11, 2024 Rob, it is a commom issue with the J's that develop over time. You were correct to clean the master switch terminals as it usually fixes the "waving" The VR detects resistance and flips on and off causing the windshield wiper effect on the ammeter.
rturbett Posted April 17 Author Report Posted April 17 heres a little late follow up- this twitching has persisted. we rebuilt the alternator with no change. I do feel better about the new brushes and diode though, so not wasted- But, I tracked the ground and when I touched it, Black wire/ pink cover it fell off the bus... cleaned it, squeezed it, reattached. Seems to have fixed it. I did impress my local mechanic.... I told him any time I had an electrical problem with a car, it was always a ground issue... I have a nice vid of the ammeter before and after, but don't know how to load it here Rob 3
PWL Posted July 3 Report Posted July 3 Rob, could you describe where the spade lugs in the photos are located. I want to check mine as well.
skykrawler Posted July 3 Report Posted July 3 Interior, left side, high above the 'eyeball' vent. There are others.
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