Ammeter and Voltage Flickering

[norcal64d]

I did a search and found some similar issues but figured I would post and see if anyone has other ideas. In flight recently I have been seeing a periodic flicker of the ammeter to the positive side. I thought it was just a gauge issue so I made sure all the timmerman nuts had good grounding contact on the gauge cluster but its still doing it. I was able to see the system voltage is from about 13.6 to 14.4 ish oscillation when its happening, and I have tried turning off as many loads as I can and them all on in flight to try to isolate it but I can't seem to find a common thread. Tonight on short final or right after landing it went rock steady with no issues till shutdown. The grounds I am thinking I need to check are the ground on the voltage regulator itself, maybe a ground on the alternator or a connection out there? Also the ground that goes from the master switch came up in other threads. Any where else to look? Right now its a minor annoyance but could develop into a problem so I'd rather not ignore it. I do have a spare voltage regulator I can install but I suspect a grounding issue since I hear a little sound in my headset when its acting up.

[gdflys]

If the voltage and ammeter are both flickering and are on different clusters or instruments and you have checked those grounds then my best guess would be the voltage regulator or overcurrent protection if there is one installed. I saw a similar issue when my VR was headed out then started dropping off completely.

[andy]

The brushes on the alternator slip rings might be worn down enough to chatter. They can be replaced without removing the alternator on most systems.

[norcal64d]

Thanks for the replies, gents. I cleaned a few grounds and flew for a 1.3 and it was rocky steady. It’s on my radar now so I’ll check the brushes the next time I have the cowling off in case that was it.

[DavZeeMXT]

I know this reply doesn’t exactly fit with the OP’s problem but maybe help someone who might read this post because their having odd ammeter displays. When my plane was parked on the ramp and hadn’t been flown in a bit my ammeter would swing back and forth like a metronome.
Now that I have a hangar with electric and keep it plugged in to a BatteryMINDer, that problem has completely disappeared. Even though the plane always started just fine, I think there was a low voltage condition that would cause it.

[RobBurson]

The brushes on the alternator slip rings might be worn down enough to chatter. They can be replaced without removing the alternator on most systems.

I suspect this may be my problem. Amp meter was going full charge full discharge in about 1 second. I took off and at 2400RPM it was fine.

Can anyone tell me where the voltage regulator is hiding?

Thanks Rob

[andy]

It's on the inside of the firewall toward the passenger side on my MX-7-180. It's actually an alternator control unit rather than a voltage regulator since it regulates the current flow through the alternator field winding. That in turn controls the voltage output of the alternator. There's a voltage adjustment screw on it. Some people use the terms "voltage regulator" and "alternator control unit" interchangeably but they're different animals electrically.

You might also check the connections on the wire that runs from the alternator control unit to the alternator field winding post on the alternator. On my aircraft there's an inline fuse near the alternator that has crimp lugs that can break or become intermittent including the one that attaches to the alternator field post. The fuse itself is the old glass AG type inside the fuse holder. It can become corroded over time and make intermittent contact.

I understand from Jeremy that newer Maules have a different arrangement to prevent the inline fuse holder lug from vibrating and breaking at the alternator but that's what happened to me years ago on my way back from Sun-N-Fun. If a connection in that wire breaks, the alternator shuts down and the low voltage warning light comes on as well as the ammeter showing a discharge.

[RobBurson]

Thank you Andy!! Have a great day.