Who pays?

First flight after annual, and the alternator light comes on over Lake
Michigan in IMC- left alternator belt thrown, which was replaced at the
annual. Never had any problems with electrics prior to this.

Replace belt, light comes on with application of power or electrical load.

Returned to mechanic- says it could be stuck counterweights on crank shaft
causing vibration that throws belts. I ask- why did this just start after
the annual, with no indication of problems prior to this?

Replace with another new belt- no change. Now note that no voltage is going
to alternator field. Diagnosis- bad voltage regulators (two), possibly bad
alternator.

Both voltage regulators removed and alternator as well. Repair shop says
they are all OK, but replaced brushes anyway.

Working diagnosis is now bad connection at alternator field wire, caused
alternator to run intermittently, and this is what threw belt initially.
Apparently, with intermittent loading of the alternator due to engine
vibrations, these pulsations caused belt to whip and jump off of pulleys.

My guess- wire was bent, kinked during initial belt change, starting cascade
of events.

Two questions: does all of this sound plausible?

Who is responsible for all of the labor, belts, and alternator and voltage
regulator check out?

Should the mechanic who changed the belt initially bear some of the
financial responsibility for this?

Who is responsible for all of the labor, belts, and alternator and voltage
regulator check out?

The shop that did the work.

Should the mechanic who changed the belt initially bear some of the
financial responsibility for this?

Yes. However, you will never, ever be able to prove any of this, so I
don't see the shop doing anything.

This is just another example of the phenomenon I've noted here before,
where something else is broken by the act of fixing (or inspecting)
something else. It's happened every time I've EVER had any work done
behind the panel.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Some good news about a shop..I recently had an overhauled DG
installed. During the install, the tube/hose to the AI was
bent, hence the AI didn't work. Shop repaired everything the
next day, no charge. Turns out the replacement DG was a problem,
shop replaced *that* one immediately, no charge. And, since I
had to leave it overnight (and my car was 30 sm away), one of
the shop people gave me a ride to the rail station (I live a block
from the end of the rail line).

When it's your tush 2-8K AGL, that $5-10/hour difference in shop time
all of a suddent becomes irrelevant.

Grr.... the dreaded "after annual anomaly"
Here's an article from Kelly Aerospace with some trouble shooting tips:
http://www.kellyaerospace.com/articl...rnator_AMT.pdf

Good luck.
Jim B

On Mar 28, 6:51 am, "Viperdoc" wrote:
First flight after annual, and the alternator light comes on over Lake
Michigan in IMC- left alternator belt thrown, which was replaced at the
annual. Never had any problems with electrics prior to this.

Replace belt, light comes on with application of power or electrical load.

Returned to mechanic- says it could be stuck counterweights on crank shaft
causing vibration that throws belts. I ask- why did this just start after
the annual, with no indication of problems prior to this?

Replace with another new belt- no change. Now note that no voltage is going
to alternator field. Diagnosis- bad voltage regulators (two), possibly bad
alternator.

Both voltage regulators removed and alternator as well. Repair shop says
they are all OK, but replaced brushes anyway.

Working diagnosis is now bad connection at alternator field wire, caused
alternator to run intermittently, and this is what threw belt initially.
Apparently, with intermittent loading of the alternator due to engine
vibrations, these pulsations caused belt to whip and jump off of pulleys.

My guess- wire was bent, kinked during initial belt change, starting cascade
of events.

Two questions: does all of this sound plausible?

Who is responsible for all of the labor, belts, and alternator and voltage
regulator check out?

Should the mechanic who changed the belt initially bear some of the
financial responsibility for this?

Am I missing something? You had an alternator problem and the A&P
decided to try the least expensive option first (the belt). When it
turned out to be something more extensive you want him to pay for the
belt? I bet 95% of the time the belt solved the problem. You could
have paid for 6 hours of labor up front to do a complete electrical
diagnostic but apparently it was decided that the belt was a good bet
for the $$$.

I cannot stress enough to new owners, you must stay very, very
involved in maintenance to avoid A&Ps spending days chasing down
things that could be done cheaper another way.


-Robert

I had no alternator problems until the mechanic doing the annual elected to
change the belt because it had some wear. Until then there had been
absolutely no problems with the electrical systems at all.

I'd ask if the first replacement belt was tensioned properly. I've
never heard of a pulsing in a perfectly good alternator cause it to lose
a belt.
Dave


Viperdoc wrote:
I had no alternator problems until the mechanic doing the annual elected to
change the belt because it had some wear. Until then there had been
absolutely no problems with the electrical systems at all.

I should have qualified that remark - I am not a mechanic but don't
overlook the obvious.
Dave


dave wrote:
I'd ask if the first replacement belt was tensioned properly. I've
never heard of a pulsing in a perfectly good alternator cause it to lose
a belt.
Dave


Viperdoc wrote:
I had no alternator problems until the mechanic doing the annual
elected to change the belt because it had some wear. Until then there
had been absolutely no problems with the electrical systems at all.

On Mar 28, 2:38 pm, "Viperdoc" wrote:
I had no alternator problems until the mechanic doing the annual elected to
change the belt because it had some wear. Until then there had been
absolutely no problems with the electrical systems at all.

I've never heard of a shop covering the cost of alternator work as a
result of replacing a belt unless you can show that they burned out
the alternator bearings as a result of the new belt. You may have too
high of an expectation of mechanics. They see something broken,
remember what fixed it the last 10 times, and do it. They don't think
a lot beyond that unless it doesn't work. That's where being involved
in the maintenance can sometimes make things work out better.

-Robert

Viperdoc - What type aircraft? Is your alternator driven from the
prop end, or the back end of the engine? If it is driven from the
back end, you have serious internal damper problems in your engine.