Can an alternator have an Intermittent problem?
Thread Starter
Race Director
Joined: Dec 2000
Posts: 17,551
Likes: 26
From: El Paso Texas
Can an alternator have an Intermittent problem?
1984 Corvette, auto, bone stock, 147K, driven about 1000 miles per year.
Took out the Vette the other day after it had sat for about 2 weeks. Cranked right up, but something wasn't right. Usually, the voltage gauge goes up to about 14.1 or so for a few minutes, then settles in around 13.1 - 13.5. This time it remained around 11 and the red charge light came on.
After about 5 minutes, it went back to normal. I drove around that afternoon, and the problem came and went. It would hover around 11.5 at road speeds, and drop to around 11 at idle. Then it would go back to charging normally for a few miles.
No belt slippage, no loose connections, etc....
Can an alternator / regulator have an intermittent charging issue, or do they just up and die? Anyone ever had this happen?
I have the alternator off and plan on getting it tested, but with an intermittent problem, couldn't it test OK and then malfunction again the second I have it back on the car?
Anything else I should be looking at? Battery is AC Delco, approx 6 months old, and never fails to start the car.
TIA
Took out the Vette the other day after it had sat for about 2 weeks. Cranked right up, but something wasn't right. Usually, the voltage gauge goes up to about 14.1 or so for a few minutes, then settles in around 13.1 - 13.5. This time it remained around 11 and the red charge light came on.
After about 5 minutes, it went back to normal. I drove around that afternoon, and the problem came and went. It would hover around 11.5 at road speeds, and drop to around 11 at idle. Then it would go back to charging normally for a few miles.
No belt slippage, no loose connections, etc....
Can an alternator / regulator have an intermittent charging issue, or do they just up and die? Anyone ever had this happen?
I have the alternator off and plan on getting it tested, but with an intermittent problem, couldn't it test OK and then malfunction again the second I have it back on the car?
Anything else I should be looking at? Battery is AC Delco, approx 6 months old, and never fails to start the car.
TIA
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Yes, I have seen them act up. Brushes can be worn on the rotors commutator and can cause the problem. Generally if a diode or a rectifier goes south, it just stops charging or if one side of the diode trio goes south the charging capacity rate is greatly reduced. If the regulator goes bad its generally bad all the time.
Thread Starter
Race Director
Joined: Dec 2000
Posts: 17,551
Likes: 26
From: El Paso Texas
Thanks for the tips. It appears to be the original alternator, so the brushes and rotating assembly are probably worn. I think I will just pop it apart tomorrow and see how the brushes look, and if they're worn, I will just replace it.
Morley, I didn't look at the connections other than just verifying that they were tight, so it's entirely possible that there's some corrosion lurking within.
In my experience, whenever an alternator goes on strike, it just quits charging. This is the first one I've had that's intermittent. I just hate replacing parts until I'm positive they're bad, and sometimes tend to over-diagnose something simple.
Thanks again for the input.
Morley, I didn't look at the connections other than just verifying that they were tight, so it's entirely possible that there's some corrosion lurking within.
In my experience, whenever an alternator goes on strike, it just quits charging. This is the first one I've had that's intermittent. I just hate replacing parts until I'm positive they're bad, and sometimes tend to over-diagnose something simple.
Thanks again for the input.
Drifting
Joined: Nov 2005
Posts: 1,361
Likes: 0
From: Downriver Mi.
You may want to switch to the newer style alt.If you do can you post what was nessecary to do the switch?I think it may just be a wiring adapter.
Last edited by MR NICE; Dec 28, 2005 at 06:20 AM.
Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
If you are on a budget it is DEFINITELY worth taking it apart and checking the brushes. Before disassembly give it a good spin while off the car to see if the bearings are still smooth. If the brushes are worn and you replace them, make sure you replace the bearings if they do not turn smoothly.
Good luck,
Good luck,
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Thread Starter
Race Director
Joined: Dec 2000
Posts: 17,551
Likes: 26
From: El Paso Texas
Originally Posted by BrianCunningham
Have you checked the fusible link? They don't burn out all at once.
Problem solved, thanks to all.
Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
So it is no surprise that the alternator failed the electrical test but did you replace the brushes or buy an AutoZone alternator?
Whenever an alternator fails to charge, it is highly likely that the brushes are simply worn out. In that case you will have a better alternator by simply replacing the brushes, and bearings if necessary, in your factory alternator than putting on an Auto Zone alternator. As a side benefit you save money. Saving money AND having a better unit on the car is a win-win deal.
Good luck with it whatever you do,
Whenever an alternator fails to charge, it is highly likely that the brushes are simply worn out. In that case you will have a better alternator by simply replacing the brushes, and bearings if necessary, in your factory alternator than putting on an Auto Zone alternator. As a side benefit you save money. Saving money AND having a better unit on the car is a win-win deal.
Good luck with it whatever you do,
Thread Starter
Race Director
Joined: Dec 2000
Posts: 17,551
Likes: 26
From: El Paso Texas
Originally Posted by MBDiagMan
So it is no surprise that the alternator failed the electrical test but did you replace the brushes or buy an AutoZone alternator?
With a few exceptions, I'm not a big believer in discount parts store stuff. I picked up a few oil filters while at Vatozone since they were nice enough to test the alternator, but I'm more confident in the Delco stuff.
