Jeep alternator

I took my 96 grand Cherokee in for a water pump replacement. The shop
said that I also had a bad alternator. It worked fine in our -20 temps
here in MN and the warning light has never come on. Do you think it
could be bad?
Thanks
Smitty

 

If your battery has not gone dead I would not replace it.

: I took my 96 grand Cherokee in for a water pump replacement. The shop
: said that I also had a bad alternator. It worked fine in our -20 temps
: here in MN and the warning light has never come on. Do you think it
: could be bad?
: Thanks
: Smitty

 

I would ask them to show you the test of your alternator in other words make
them load test it in front of you if won't show you go some where else.

 

Install a voltmeter gauge and watch it yourself. If it shows >13.5 volts
at idle and >14 volts on the highway, the alternator's fine.

 

thanks I just now did that. The load test showed 11v and the "new" one did
too. I'm thinking that there is some external regulator that needs to be in
the circuit. Very strange. I don't know what to think now.
Smitty

 

Certainly. The mechanic probably gave it a spin after having removed the
belt to change the water pump, and detected a rough bearing, indicating
impending alternator lockup. Such an alternator usually charges just fine
right up to the instant it locks up and causes big problems.

DS

 

Let me share a story which will help illuminate the matter:

At one time, I drove a very used 1991 ex-police Chev Caprice. One very
cold winter morning, I noticed a new noise from under the hood. Faint, but
present. Sort of an intermittent hissing/clicking sound coming from the
front. I carefully homed in on the alternator as the source of the noise
and made a mental note to replace it, for obviously one or both of its
bearings had begun to fail.

But life being what it is, I didn't get around to it. Working on cars is
very little fun in the winter, and the alternator was continuing to
charge. I fed a few drops of oil into the front bearing via the shaft and
kept on driving, periodically reminding myself that I ought to look at
changing the alternator. Eventually I pretty much forgot about it.

About 2 months later, I was on the highway doing about 65mph when a sudden
loud noise began to emanate from up front. It sounded like the moan of a
dead power steering pump, but it obviously wasn't, for I still had
steering boost. The noise rapidly grew louder and evolved into a
hair-raising grinding noise. The voltmeter dropped, the "AMP" light came
on, and the smell of very hot metal filled the car. The alternator's front
bearing had locked up solid, and the entire bearing was now spinning in
its interference fit, meant to keep the bearing's outer ring stationary in
the alternator's front housing.

It was still about 3 miles to the next exit. I decided to go for broke,
and kept on driving. The grinding sound got ever louder, the stink of
broiling metal grew heavier and hotter. I pulled off the highway at the
first opportunity, and found...nothing. No service station, no phone
booth, just an intersection.

Back on the highway, another mile down the road, I pulled off at the next
exit, into a gas station's parking area and killed the engine. I yanked
the hood release, lifted the hood, and a thick column of smoke poured up
from the *extremely* hot alternator. The once-greasy painted brackets were
now bare steel, dark pink in color. I ran into the convenience store,
bought a bottle of water, sprinted back outside and carefully poured it
over the alternator. The water instantly and loudly flashed into steam. I
bought another bottle of water, and another. By the time I had poured the
third litre of water over the alternator, it was merely fizzing rather
than flashing the water directly into steam.

There was a parts store with a service department one block down the road,
so I got back in the car and started the engine. The water treatment had
averted fire danger due to extreme heat, but in the time it had taken me
to buy the first bottle of water, the alternator had welded itself solid.
The 3-month-old serpentine belt skidded over the locked-up alternator
pulley and cooked itself to death in a big cloud of noxious smoke
during the one-block drive to the service center.

Three hours and $250 later, the car had a replacement alternator and a new
belt, both of unknown quality.

If this is your idea of a fun diversion during an important trip on an
unpredictable day, by all means ignore your mechanic.

If it isn't, ask him to be more specific about what's gone bad in the
alternator. I'm betting he gave the alternator a spin when he removed the
belt to replace the water pump, and felt a rough bearing.

DS

 

Smitty posted a little earlier that both old and new alternators load
tested at 11V - so it sounds like something else is going on external to
the alternator.

Anyway - while we're telling war stories, I had a similar alternator
lock up on an '88 DeVille - my wife was driving by herself at the time.
She had to walk 1/4 mile to get me. So we drive back to it in my
car. The dust being thrown from the serpentine belt downstream of the
alt. pulley piled into a handy little crevice on top of the engine.
When I opened the hood, the pile of rubber dust was glowing red, just
like embers in a fireplace. Really weird and amazing.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

 

YAWN

 

1) The load test results say nothing about the condition of the bearings.
2) It's entirely possible the load test was not done correctly.

Fun and amazing after the fact...scary and damned inconvenient at the
time!

 

But...if the load test is correct, then there's no reason to assume it's
the bearings. But we're both speculating about something we can't prove.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

 

That sounds like they noticed something physical like a worn bearing.

One test is to start it up and feel the alternator. When bearings are
about to fail, they usually heat up the alternator case fast and they
usually cause a vibration you can feel.

Another test is to remove the fan belts and hand rotate the alternator
to feel for bearing grab or play in the shaft. If there is any shaft
play, suspect a bearing.

Then you have your common, 'he is getting off too cheap with a belt,
lets see what else we can sucker him for' ploy. This seems to be
happening more and more these days as cars get more complicated.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

<snip novel>

 

Sure there is: The tech said the alternator is going bad.

 

Thanks for all your replies. The tech said nothing about the bearings. I
watched him do the load test. Both the new one and the old one had the same
output of 11V. I'm thinking that this unit has a voltage regulator that is
separate from the alternator itself and there is some thing inside the
alternator that keeps it from going too high with out the external
regulator. On the vehicle the output tested low also, although I did not
see him test it. I left the shop (not a Chrysler shop) with these words. If
you think the new one will work put it on. He said he would and that he
would check it after it was installed. If it did not work he said that he
would put the old one back on. My wife picked up the car with a new
alternator. I have not had a chance to check it myself for output but I will
this weekend. The whole thing is still a little of a mystery but thanks to
everyone who replied.

My wife just drove in with the car while I was typing this. I just checked
it out with the new alternator installed. Engine off- the battery measures
12.4V Running it checks 13.9V so I guess all is well. I may never know if
it really needed a new alternator but I'll have to take their word for it.
They have always done the right thing in the past so I guess It's a done
deal.

Thanks again,
Smitty

 

No - the OP said: "The shop said that I also had a bad alternator"
(check the original post) as in "already bad". That doesn't imply bad
bearings any more than bad electrical output. Not quite the same as the
shop saying it was "going bad".

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

 

I'm curious Dan. Since the alternator was cooked, was there any core
trade-in value on it towards the new one?

-Kirk Matheson

 

Well.... The regulator is in the computer, not the alternator shell but
still......

I really have a hard time buying a 'dead' alternator suddenly when you
get a belt changed, especially after all the recent cold weather and you
having no issues.....

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

 

they might have found with the belt off the alt. pulley is noisey like it has a
bad bearing

 

8< 8= 8< 8= 8< 8=

8< 8= 8< 8= 8< 8=

8< 8= 8< 8= 8< 8=

8< 8= 8< 8= 8< 8=

That's the funny part -- there was not a SINGLE usable piece on that
alternator. The rotor, stator and all other internals were thoroughly
barbecued and the housings had sustained severe heat damage (rear) and the
spun bearing (front). Nevertheless, Canadian Tire did deduct the core
value from the final bill. A very expensive doorstop for a remanufacturing
plant somewhere.

 

I can't remember the last time I had a core inspected -- it seems like
the rebuilders have decided it isn't worth trying to get retailers'
counter people to fight with customers over the value, and just accept
that a certain percentage of their cores will be worthless.

I've got a steering box on the way from Firm Feel (it wasn't the
pump... wish I'd seen Steve's email about testing it before I had the
replacement on special order), and they've promised me the core value
on my old box sight unseen.