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Tail fairing repair, and alternator replacement at bruceh's hangar

SPX

Well Known Member
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On Thursday, I flew over to bruceh's hangar with a tail repair task in mind. Short story is, while the hangar was being maintained by the landlord, the hangar door and the vertical stabilizer of my RV had a little disagreement, and the door won. Fortunately, the damage was quite minimal, and was taken care of by replacing the vertical stabilizer fairing (PN VS-909).

You can read about the repair, and see some photos on Bruce's blog page.

So, I said that I flew over with the tail repair task in mind. If you skipped ahead and read Bruce's blog, then you know where this is going. We all know one thing leads to another.. on the flight prior, the voltage while flying would vary between 13.7 and 12.5'ish volts. By vary, I mean it would be 13.7 one minute, and then it would wander down to the 12.5 range, and then climb back up. This was not really the typical alternator failure scenario that I am familiar with. Battery voltage was not dropping, and I wasn't exactly sure what the problem was..indication, connection, or the alternator itself.

When I started up the motor for the flight over to see Bruce (~12 minutes), I had pretty good voltage of 13.9 or so, through startup, runup, and takeoff. Right after liftoff, the cycling between battery volts and the mid to high 13 volt range started again. Hmm.. are vibrations causing an intermittent connection? On the descent, the voltage only fluctuated once. And from pattern entry to taxi in, the voltage was reading good from the alternator. But now I've determined that the problem seems to appear when at higher power settings.

As Bruce was working on the tail, I uncowled the airplane and looked around at the few connections there are for the alternator. Nothing really stood out. With no findings, we decided to roll the dice, and consider an alternator change. I knew I wasn't likely to find an aviation alternator nearby, but both Bruce and I had heard of auto alternators being used in the past. With a little VAF searching, I learned about some alternators that would fit. Tried looking for the alternator by the Lester number. The number returned results, but no stock (they could have the alternator by Tuesday.. five days away). I then asked for an alternator for a 1995 Suzuki Samurai, rather than by the Lester number. Bingo! In stock. Armed with measurements of the existing alternator, and some photos, off I went to O'Reilly Auto Parts to take a look.

I arrive at the auto parts store, and the alternator is pulled off the shelf for me. Looks like it'll work. $80 or so later, I am out the door, and on my way back to Bruce's hangar.

Back at the hangar, Bruce and I begin the process of removing the existing alternator. For proper access, a bit more than the alternator had to be removed, but it wasn't terrible. It quickly became apparent that not only had I found a compatible alternator, I had actually found an identical alternator to one that we were removing. With it being identical, the install was fairly straightforward. We did have to move a bushing that was protruding in the wrong direction, and therefore was interfering with securing the alternator to the existing bracket. A hammer fixed that problem. Shortly thereafter, the alternator was installed. And it was time for testing..

First engine run showed battery voltage only (a change in the wrong direction, because the old alternator would at least show good voltage on the ground). Bruce and I both simultaneously came up with the thought of moving the voltage sense wire, because Bruce wasn't 100% sure if it had been removed from the inner or outer vertical spade tab. Our first guess was wrong, so we switched the connector to the other tab, and did another engine run. Viola, 14.2 volts. We cowled the airplane, and I flew it home.

On the flight back to my hangar, the voltage was good. Today, I flew 1.2 hours over three legs, and never saw voltage below 14.1, and it was mostly 14.2. So, I feel confident saying the problem was fixed.

I've been curious about the 13.7 voltage that I had seen "forever," because I really would hope for 14+ volts. However, for as long as I can remember, the voltage has been in the mid to high 13 volt range. Given the newly installed alternator never drops below 14 volts, I think this was a slow failure that finally showed itself a lot more obviously. Moving forward, I know to look at dropping voltage below 14 is likely the sign of an impending failure. Why the alternator worked at low power, but not so well at high power, we did not determine. I'd guess something to do with the internal voltage regulator, or maybe a connection internally.

Time before failure: 300+ hours (alternator was used when it was installed at 0 hours, and unknown how many hours it had accrued prior to being installed on my RV. For all I know, it is possible that it was removed from the last install due to voltage < 14 and it has never been above 14 since day 1 on my RV)

Alternator: AutoZone part number R111413A. Fits 1995 Suzuki Samurai 1.3L.
 

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