PERSISTENT Electrical System Pulsing

[jaylw314]

22 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. 

How does the alternator kick offline if the CB doesn't pop?  Do you actually get an undervoltage and how much?

I might suspect something in the wiring like a fatigue break in the alt field wire to the master switch from poor strain relief.  That would explain the sequence of symptoms of a high resistance connection there, proceeding to complete inop of the alternator (assuming that is the case)?

[Davarron]

8 hours ago, jaylw314 said:

How does the alternator kick offline if the CB doesn't pop?  Do you actually get an undervoltage and how much?

I might suspect something in the wiring like a fatigue break in the alt field wire to the master switch from poor strain relief.  That would explain the sequence of symptoms of a high resistance connection there, proceeding to complete inop of the alternator (assuming that is the case)?

You win the prize of the day! My mechanic tonight, along with an electrical engineer, found the break in current between the alt field CB and the master switch. Replacing this wire completely fixed the pulsing issue and the alternator offline issue (according to the ops runup. Will find out for certain next time I fly it soon). This 16 gauge wire did not just break according to my mechanic. Since the problem began after I had the avionics installation done a few months ago, he believes the avionics shop is the culprit. Adding this to the list of other issues from this "shop", I would not hesitate for a second that it was caused by them (obviously not intentional, however, there is a level of detail and care that must be taken on these older airplanes. Carelessness has no room here).

[jaylw314]

1 hour ago, Davarron said:

You win the prize of the day! My mechanic tonight, along with an electrical engineer, found the break in current between the alt field CB and the master switch. Replacing this wire completely fixed the pulsing issue and the alternator offline issue (according to the ops runup. Will find out for certain next time I fly it soon). This 16 gauge wire did not just break according to my mechanic. Since the problem began after I had the avionics installation done a few months ago, he believes the avionics shop is the culprit. Adding this to the list of other issues from this "shop", I would not hesitate for a second that it was caused by them (obviously not intentional, however, there is a level of detail and care that must be taken on these older airplanes. Carelessness has no room here).

It would be interesting to know where the wire broke, whether it was in the wire body or at one of the terminals/crimps.  Glad it looks like a curable problem!