warning light on... alternator revision??

warning light on... alternator revision??

Joined: November 5th, 2005, 8:22 pm

August 22nd, 2008, 7:43 am #1

Hi guys,

my alternator is making a subtle rattling sound, which came to the light when I was checking why the battery-warning light was on, not fully, bit it was on alright everey now and then. As the leads and connections seem OK, and there is a rattling sound coming from the alternator area, I suspect it is broken.

Does anybody have an idea what is wrong, could it be a broken bearing, and could I fix it myself or should I visit a alternator revision mechanic..

Anyhow, thanks in advance!

Frank

Frank Jacobs
Holland, Utrecht
1977 Fiat X1/9 1300
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///Mike
///Mike

August 22nd, 2008, 9:20 am #2

The rattling sound may or may not be related to the alternator light. For example, bad bearings alone should not cause the light to come on. Besides, bearings usually make a whirring/grinding sound when they're about to go. Rattling sounds more like a loose pulley or bent fan.

In my experience the most common cause of an alternator light being on is a resistive connection between the alternator and the battery. The connections can look okay, but still not be carrying enough current. That's what's happening when the alternator light glows when the high beams, A/C (or heater), and wipers are on (in other words, high electrical load). Adding a second wire between the alternator and the starter will solve that.

If your alternator light comes on at random the brushes in the alternator may well be worn out. That might even account for some of the noise. I would suggest listening to the alternator while under load with a mechanic's stethoscope. Or just pull it and have a really good alternator/starter shop check it for you-- they're not that difficult to remove.

BTW, if the brushes are worn out then continuing to run the motor will result in the slip rings being worn beyond repair. Best to find the root caue ASAP.

HTH,

///Mike
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Joined: November 5th, 2005, 8:22 pm

August 22nd, 2008, 1:03 pm #3

Rattling may not be the best word for it.. Sitting inside the car, when idling, the sound most reminded me of sparking, when a connection is not OK, but this was not the case, at least not from the OUTSIDE... I think I'd best dismantle the alternator, worn bearings should come to light then right? turning the pulley should reveal the real problem

BTW, the fan and belt seem ok, not slipping at all.

Thanks a lot for your input!

Frank

Frank Jacobs
Holland, Utrecht
1977 Fiat X1/9 1300
Quote

///Mike
///Mike

August 22nd, 2008, 9:08 pm #4

The noise you describe could well be worn bearings. Might still be worn brushes too. Listening through a stethoscope or a long handle screwdriver helps confirm where the noise is coming from. You can often identify which component is noisy that way.

The pulley and fan are locked to the shaft by a Woodruff key. I've seen instances where the key slot on the fan becomes worn and it rattles as it moves back and forth, even though the pulley is still locked in place. But probably not your problem from this later info.

If it turns out the noise is from a bad bearing or bearings then you should also look for another problem-- bad bearings should not cause the charge light to come on unless they're so bad the belt is slipping. Bad brushes are the most likely cause of both noise and the charge light.

Good luck and let us know what you find.

///Mike
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jake
jake

August 23rd, 2008, 3:25 am #5

Hi guys,

my alternator is making a subtle rattling sound, which came to the light when I was checking why the battery-warning light was on, not fully, bit it was on alright everey now and then. As the leads and connections seem OK, and there is a rattling sound coming from the alternator area, I suspect it is broken.

Does anybody have an idea what is wrong, could it be a broken bearing, and could I fix it myself or should I visit a alternator revision mechanic..

Anyhow, thanks in advance!

Frank

Frank Jacobs
Holland, Utrecht
1977 Fiat X1/9 1300
the pivot bolt for the alternator had backed out. it was far enough for the alternator to be loose on the belt and rattle around.
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Joined: November 5th, 2005, 8:22 pm

August 23rd, 2008, 11:13 am #6

The noise you describe could well be worn bearings. Might still be worn brushes too. Listening through a stethoscope or a long handle screwdriver helps confirm where the noise is coming from. You can often identify which component is noisy that way.

The pulley and fan are locked to the shaft by a Woodruff key. I've seen instances where the key slot on the fan becomes worn and it rattles as it moves back and forth, even though the pulley is still locked in place. But probably not your problem from this later info.

If it turns out the noise is from a bad bearing or bearings then you should also look for another problem-- bad bearings should not cause the charge light to come on unless they're so bad the belt is slipping. Bad brushes are the most likely cause of both noise and the charge light.

Good luck and let us know what you find.

///Mike
Hi Mike, thanks a lot for your help.

I checked the things you suggested as far as I could with the alternator still in the car,and found no excessive play or slipping belt.

Therefore, I started with disconnecting the leads to the alternator and found the groundcable to be worn to the bone, and one of the other leads, probably directing the current to the battery was badly worn at the connection end. Fixed these wires, and the problem including the subltle sound are gone.

Guess it was sparking what I heard after all.. The light stays off, even under heavy load (high beam/windscreen wipers etc, which was the case before.

Thanks again for your advice!

Frank Jacobs
Holland

Frank Jacobs
Holland, Utrecht
1977 Fiat X1/9 1300
Quote

Joined: November 5th, 2005, 8:22 pm

August 23rd, 2008, 11:17 am #7

the pivot bolt for the alternator had backed out. it was far enough for the alternator to be loose on the belt and rattle around.
that has happened to me before, few months ago, but then it turned out to be that the bracket, holding the alternator in place was completely shot. The alternator was really hanging loose on the belt.

But this time, it were the wires that were badly worn. fixed that and solved the problem.

Thanks for your input!

Frank Jacobs
Holland

Frank Jacobs
Holland, Utrecht
1977 Fiat X1/9 1300
Quote

///Mike
///Mike

August 23rd, 2008, 7:33 pm #8

Hi Mike, thanks a lot for your help.

I checked the things you suggested as far as I could with the alternator still in the car,and found no excessive play or slipping belt.

Therefore, I started with disconnecting the leads to the alternator and found the groundcable to be worn to the bone, and one of the other leads, probably directing the current to the battery was badly worn at the connection end. Fixed these wires, and the problem including the subltle sound are gone.

Guess it was sparking what I heard after all.. The light stays off, even under heavy load (high beam/windscreen wipers etc, which was the case before.

Thanks again for your advice!

Frank Jacobs
Holland

Frank Jacobs
Holland, Utrecht
1977 Fiat X1/9 1300
Must have been quite a bunch of arcing for you to be able to hear it in the car. Glad you got it fixed and that it didn't cause any further damage.

Thanks for letting us know.

Regards,

///Mike
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