Jeep alternator

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

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.

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

"Daniel J. Stern" wrote:

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')

Faint, but

stationary in

rather

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

Smitty wrote:

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.