Ammeter twitching

[rturbett]

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]

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.

[geoffb]

clean and tighten the spade connector on the back of the ammeter field switch.  Terrible application for a spade terminal.

[Yetti]

measure voltage with plane running with digital VOM.   Check Grounds to the instrument cluster.   Report back.

[231LV]

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]

The M20J has a Lycoming. Belt drive alternator - no coupler.

[rturbett]

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]

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. 

[Ethan]

Could it be the draw on your system of the strobes (LED or Xenon)? My ammeter twitches each time my LED strobes fire.

[rturbett]

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]

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.