Alternator

[william myers]

Has anyone ever seen this sudden problem with the alternator? It
charges up to about 1500 rpm, then goes to zero. Kicks back in about
1000 rpm and charges fine at low rpm. I've changed the regulator and
the brushes. Thought the brushes would fix since new springs were
'bout 3/8 longer than old ones, but not so. Seems to be independent of
load. Sure hate to spend $$$ on rebuilt alternator (80 Amp).

Thanks for any help,
Bill '74 Glacier.

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[travis martin]

> Has anyone ever seen this sudden problem with the alternator? It
> charges up to about 1500 rpm, then goes to zero. Kicks back in about
> 1000 rpm and charges fine at low rpm. I've changed the regulator and
> the brushes.

Be sure that the nut is tight on the pulley. The pulley is not keyed to the
shaft; it is designed to slip if a bearing seizes. Under the nut is a wave
washer to provide friction to the pulley, but the nut needs to be tight.
What can happen is that as the alternator speeds up, it puts out more
current, requiring more torque to drive it...then the pulley slips.

Can't guarantee that this is your problem; I'm not there. But it's a good
place to look, and you've already changed brushes and regulator.

Travis in Lubbock, Texas

 

[william myers]

Thanks all for the inputs on my alternator voltage vs rpm problem. The
isolator is new (perhaps there's a clue). I have some new things to
check when the weekend arrives.

Bill ... on the digest ...

clip --------
Bill - it might be the built in regulator in the alternator. Again, it
might be the battery or the motorhome isolator. First check your
battery.
If necessary put a known good battery in for the test. Then take
thecenter lead from the isolator and connect it to one of the side
leads thatgoes to ....
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