PERSISTENT Electrical System Pulsing

[Davarron]

Merry Christmas all!

Over the summer I had a G5, Lynx xpdr, and a PMA450B audio panel put in. Soon after the installation, related or not, my ammeter and voltmeter started pulsing after engine startup until engine shutdown. The voltmeter would bounce from like 13.0 to 15.5 volts or so continuously. Flying at night, the lights dim and bright with the pulsing. It's definitely not an indication issue. My mechanic and I are stumped. We have put a new alternator, new voltage regulator, new master switch, new alternator 70A circuit breaker, new alternator field 5A circuit breaker. Nothing seems to help. And we have tried isolating everything in the cockpit regards to avionics and stuff and cannot isolate anything. 

Any ideas???

I've read on here something about a shunt past the ammeter. I'm not too familiar with it. Can anyone think of anything else to check or do or replace? A ground issue, which I'm afraid of it being, could take days of labor to find.

Thanks for the input

[Niko182]

You didn't state replacing a battery? also try pulling all the avionics circuit breakers out. I'd try pulling all of them and see if it stops. if it does, start pulling individual ones.

[Davarron]

Good idea on both. The battery is a Concorde xc and is about 2.5 years old. It shows no sign of even starting to show diminished life. Could the battery be an issue?

[RLCarter]

With the volt & amp meters jumping around along with lights dimming at the same time sound to me you have a partial short to ground. Voltage spikes can take out spendy electronics, if it were me I'd contact the ones that installed the new avionics.

[cbarry]

Can you tell if the pulsing is in sync with the transponder “reply” pulse?

[Davarron]

36 minutes ago, cbarry said:

Can you tell if the pulsing is in sync with the transponder “reply” pulse?

It does it immediately upon engine start before I even turn the avionics master on. The only thing on at that point would be the G5 I think. 

[Niko182]

pull the CB of the G5's.

[Guest]

It sounds like classic alternator field switch failure, but you’ve already replaced it.  How are the wire terminals on the switch?  Loose connections lead to high field resistance and unsteady alternator output.  You can re crimp the terminals then reinstall them on the switch.

Clarence

 

[mike_elliott]

Clean the terminals on the master switch. The resistance is giving the V/R "bad data" and causing it to charge, oh wait a minute, no charge, oh wait, better charge....fairly common on J's.

PTK, isn't that what you "resisted" doing that fixed yours also a year or 2 ago?

 

[Davarron]

1 hour ago, mike_elliott said:

Clean the terminals on the master switch. The resistance is giving the V/R "bad data" and causing it to charge, oh wait a minute, no charge, oh wait, better charge....fairly common on J's.

PTK, isn't that what you "resisted" doing that fixed yours also a year or 2 ago?

 

The master switch is brand new so I would assume the terminals should be new as well?

[Davarron]

2 hours ago, M20Doc said:

It sounds like classic alternator field switch failure, but you’ve already replaced it.  How are the wire terminals on the switch?  Loose connections lead to high field resistance and unsteady alternator output.  You can re crimp the terminals then reinstall them on the switch.

Clarence

 

Which switch are you referring to? The master switch is the combined battery and alternator one. I can have my mechanic take a look again behind the panel there but he said he had verified everything was good. 

[Yetti]

Check all the frame grounds and make them shiny bright point to point contact.  Also clean the battery terminals.   One by the battery.  STrap to the engine.   Check all wiring between the regulator and alternator.  Sounds like one is hanging on by a strand.   Check the B+ cable lug on the alternator for corrosion/loose terminal

[Yetti]

check the alternator mounting bracket for tightness.  check belt for proper tension.  check alternator for broken mounts

[Guest]

6 hours ago, Davarron said:

Which switch are you referring to? The master switch is the combined battery and alternator one. I can have my mechanic take a look again behind the panel there but he said he had verified everything was good. 

The master switch is a double pole switch, one half is the master, the other half is the alternator field switch.  Some of these are are push on spade terminals not screw on terminals.  Check that the female spade terminal ends on the wires grip the males terminal on the switch tightly.

Clarence

[flyboy0681]

Did the AMMETER look like this? If so, it's the master switch terminals, at least it was for me.

[Davarron]

31 minutes ago, flyboy0681 said:

Did the AMMETER look like this? If so, it's the master switch terminals, at least it was for me.

That is EXACTLY what mine is doing. Along with the voltmeter on the jpi. 

[jaylw314]

Reach under the panel when the master switch is on and jiggle the wires and connectors leading to the switch.  If the pulsing stops or changes, you have your culprit.

@flyboy0681's video rings true--a number of us have had that issue.  I just had my shop clean the contacts, check if any connectors need recrimping and tighten the connectors, and the problem goes away like magic

[flyboy0681]

18 minutes ago, jaylw314 said:

Reach under the panel when the master switch is on and jiggle the wires and connectors leading to the switch.  If the pulsing stops or changes, you have your culprit.

@flyboy0681's video rings true--a number of us have had that issue.  I just had my shop clean the contacts, check if any connectors need recrimping and tighten the connectors, and the problem goes away like magic

 

What he said.

[zerotact]

I originally had something similar, and found a bad Diode when I took the alternator in to get tested...    Fast forward two or more years later, the plane was sitting getting a new engine,  At overhaul a Plane power unit was installed.   The plane was fine during test flights, then parked. One of the next flights, the gauges are dancing all over, it gets worse with more load, and the ammeter looks like its vibrating its moving so fast.  No I too am back to square one, I doubt my alternator is the culprit.  Its cold so I have not pulled it out and test ran the engine after pulling and reseating the wires to the master switch and the cannon plug to the VR...   Is there other things to look at or is my faster needle wiggle something completely different?

[N201MKTurbo]

I had the same problem reciently. I did everything everybody is talking about. I changed brushes, cleaned the master contacts. I even disassembled the alternator and inspected the diodes and field connections. 

It turned out to be the regulator. I replaced it with a Ziftronics and now it works perfect.

[zerotact]

I just test ran mine and my gauges hold steady now... i reseated all the wires on the master switch, cannon plug to the regulator and the ground wire in the regulator circuit 

[Davarron]

Update: The ammeter and voltage swinging has gotten worse and now the alternator kicks offline in flight. Resetting the field CB reset it. However, on the most recent flight, the alternator kicked offline and I was not able to get it back online at all. Even after landing and restart, still offline. I wish it was as easy as the VR. But that's new, the alternator is new, the master switch is new, everything is tight and cleaned. My mechanic is going to jump across the shunt. Will report back if that works. 

[LANCECASPER]

16 hours ago, Davarron said:

Update: The ammeter and voltage swinging has gotten worse and now the alternator kicks offline in flight. Resetting the field CB reset it. However, on the most recent flight, the alternator kicked offline and I was not able to get it back online at all. Even after landing and restart, still offline. I wish it was as easy as the VR. But that's new, the alternator is new, the master switch is new, everything is tight and cleaned. My mechanic is going to jump across the shunt. Will report back if that works. 

Do not attempt to re-set the alternator CB more than one  time in flight. What's worse than the ammeter and voltage swinging? An in-flight electrical fire.

[RLCarter]

17 hours ago, Davarron said:

Update: The ammeter and voltage swinging has gotten worse and now the alternator kicks offline in flight. Resetting the field CB reset it. However, on the most recent flight, the alternator kicked offline and I was not able to get it back online at all. Even after landing and restart, still offline. I wish it was as easy as the VR. But that's new, the alternator is new, the master switch is new, everything is tight and cleaned. My mechanic is going to jump across the shunt. Will report back if that works. 

 

51 minutes ago, LANCECASPER said:

Do not attempt to re-set the alternator CB more than one  time in flight. What's worse than the ammeter and voltage swinging? An in-flight electrical fire.

I wouldn't even fly it without knowing what was causing the problem, I would also think the spikes can't be good for the radios and other electronics 

[Davarron]

I should have clarified..the CB never popped. I pulled it and reset it, which made the alternator come back online again. But I definitely agree with you not to do it more than once. Hopefully we get it figured out soon.