Alternator mystery solved
 

I asked here last summer about intermittent static and chirping from the
engine alarm buzzer. Lots of theories, loose belts, flakey wiring, etc.
The problem came and went and then cleared up.

I asked the local boatyards for the alternator "go to guy" in the area and
took it in. Before both my feet were across the threashold he said, "Oh, a
Yanmar!"

I told him I was bringing it in for checking and about the static from the
alarm speaker. He said, "You've got bearing issues." I handed him the
alternator and he wiggled it so I could hear the faint click, click and
said, "Yup. Rear bearing."

The bearing wears and allows enough movement for the rotor to hit the
stator. It first hits very lightly on the closest part making the chirping
and static. The high spot sometimes gets knocked off and the the sound
stops. The bearing wears some more and it starts again. Eventually, the
contact becomes enough to stop the charging system. By that time, the
stator or rotor are usually worn enough that the unit has become a
paperweight. Since mine was still charging fine, it may be repairable.
I'll know in a couiple of days.

I asked if I should undertake the very difficult job (on my boat at least)
of renewing all the wiring and he said, no, this was definitely the cause of
the noise I was hearing.

--
Roger Long

Alternator mystery solved
 

"Roger Long" wrote in message ...
I asked here last summer about intermittent static and chirping from the
engine alarm buzzer. Lots of theories, loose belts, flakey wiring, etc.
The problem came and went and then cleared up.

I asked the local boatyards for the alternator "go to guy" in the area and
took it in. Before both my feet were across the threashold he said, "Oh, a
Yanmar!"

I told him I was bringing it in for checking and about the static from the
alarm speaker. He said, "You've got bearing issues." I handed him the
alternator and he wiggled it so I could hear the faint click, click and
said, "Yup. Rear bearing."

The bearing wears and allows enough movement for the rotor to hit the
stator. It first hits very lightly on the closest part making the chirping
and static. The high spot sometimes gets knocked off and the the sound
stops. The bearing wears some more and it starts again. Eventually, the
contact becomes enough to stop the charging system. By that time, the
stator or rotor are usually worn enough that the unit has become a
paperweight. Since mine was still charging fine, it may be repairable.
I'll know in a couiple of days.

I asked if I should undertake the very difficult job (on my boat at least)
of renewing all the wiring and he said, no, this was definitely the cause of
the noise I was hearing.

--
Roger Long



Best of luck Roger. Here it does not cost all that much to rebuild an alternator time is more of an issue.

Alternator mystery solved
 

On Mon, 10 Nov 2008 13:33:53 -0500, "Roger Long"
wrote:

I asked here last summer about intermittent static and chirping from the
engine alarm buzzer. Lots of theories, loose belts, flakey wiring, etc.
The problem came and went and then cleared up.

I asked the local boatyards for the alternator "go to guy" in the area and
took it in. Before both my feet were across the threashold he said, "Oh, a
Yanmar!"

I told him I was bringing it in for checking and about the static from the
alarm speaker. He said, "You've got bearing issues." I handed him the
alternator and he wiggled it so I could hear the faint click, click and
said, "Yup. Rear bearing."

The bearing wears and allows enough movement for the rotor to hit the
stator. It first hits very lightly on the closest part making the chirping
and static. The high spot sometimes gets knocked off and the the sound
stops. The bearing wears some more and it starts again. Eventually, the
contact becomes enough to stop the charging system. By that time, the
stator or rotor are usually worn enough that the unit has become a
paperweight. Since mine was still charging fine, it may be repairable.
I'll know in a couiple of days.

I asked if I should undertake the very difficult job (on my boat at least)
of renewing all the wiring and he said, no, this was definitely the cause of
the noise I was hearing.

A good local alternator shop can frequently upgrade your charging
capacity by installing after market high capacity stators, diodes and
bearings. I recently ended up with a pair of 160 amp units that way
at about 1/3rd of Balmar's pricing.

Alternator mystery solved
 

Denis M wrote:

Best of luck Roger. Here it does not cost all that much to rebuild an
alternator time is more of an issue.

Thanks. I'm optimistic because it was still charging. He said that they
are often dead by the time the charging light comes on and the batteries
stop charging because the rotor is so worn that it is out of balance or the
stator is ruined. The little alarm buzzer provides earlier warning than the
light because it broadcasts the static created by the first light contact
between the rotating parts.

I'll know for sure in a couple of days. I don't need to put it back on the
engine for about four months so time isn't an issue:)

--
Roger Long