91 caprice 5.0L SBC V8 alternator

Joined
Oct 6, 2014
Messages
251
Location
Minnesota
Hi glorious and wonderous peoples of BITOG. : P I remain ever grateful for the people who share their knowledge and opinions...


I have a 91 chevy caprice classic, TBI 5.0L V8 which i assume needs an alternator. The only way that I know this is that in the middle of winter when it was 20 below I tried driving it and all the sudden the battery/charge light started flickering and lighting up... and that it's 31 years old/pretty sure the alt has never been replaced. I parked it for the moment (driving my 11mpg pickup instead not being up to a mid-winter wrench job) but finally got it out of a snowbank with rising temperatures literally yesterday. It had been started 2-3 times in jan/feb to see if it would keep the battery charged up - and it actually did, ran 20+ minutes fine (tho I wasn't watching the light, I just started and left it while shoveling snow to see if it'd die or live).

Now that it's out of the snowbank it did fine on two test drives around town for 30 miles in 20 degree temperatures, i'll doublecheck it at an O'rielly's or something but even if it passes the alt test I can think of no reason the battery/charge light would come on. (this has only idiot lights, no gauges so I can't watch for flickers or such) So I don't trust it. I'd rather wait until summer but I have to drive this out of town overnight so a breakdown would suck.

I assume the default answer will be just replace it, just wondering if anyone has any other advice. Like on amazon I see "other" small block chevy V8 alternators for cheaper than the ones they recommend, but maybe I should stick with those it recommends for my car... Amazon has AC Delco for $90ish, Rock Auto has some for a little less, i'm just curious if there's any caveats or "if youre changing X you might as well change Y at the same time" things. (not looking to do a waterpump, but a new serpentine belt probly makes sense/I don't remember when I last changed it)

I realize i'm asking some questions that might have obvious answers but i'm a TBI survivor and that's what it's like now, sorry if I need some handholding or walking through the process.
 
Joined
Jun 19, 2019
Messages
766
Location
Missouri
I would put a little more time in to diagnosing the issue before jumping straight to replacing the alt. Was the battery also tested at the parts store?

If you do need to get a new alt, I usually prefer to get a lifetime warranty reman'd unit from a parts store. You may have to sort through a dud or two, but if that alt goes out later down the road, the subsequent replacements are free and usually in stock. To me, it's worth it to pay a little bit extra to not have to wait for the two-way shipping to get a replacement.
 
Joined
Jun 15, 2003
Messages
38,605
Location
ME
Sounds like a sticky brush. It might clear itself with more frequent driving.

The most basic test is to throw a voltmeter on the battery when idling, to see if you're getting 14-15.x.

If you're driving with the heater fan on, you'll notice a voltage drop with a change in fan pitch. Ears are very good for this. You can also get cheapo digital volt meters that plug into your cigarette lighter.
 
Joined
May 7, 2004
Messages
13,185
Location
Nokesville, VA
Sometimes a loose or slipping belt will cause the alternator light to turn on. Especially if it's flickering. I've had that happen before. The bearings in the tensioner for the alternator belt were shot. Lots of play. New tensioner fixed it.
 
Joined
Nov 22, 2004
Messages
9,057
Location
Texas
Alternators will fail/breakdown at higher temps so due to the cold weather I doubt you will see this condition again until it warms up. With that, it still is a good idea to test the alternator, all cables and connections and even the battery.
 
Joined
Mar 31, 2010
Messages
6,067
Location
Iowa
If you do decide to replace it, make sure the battery is healthy and fully charged. Also inspect the belt with a gauge and tensioner - give it a spin and listen to the bearings. Any noise, replace
 
Joined
Feb 27, 2006
Messages
3,482
Location
Cincinnati
AC-Delco reman's are nothing to write home about, GM sold it's Delco-Remy Division off long ago.

I would have it rebuilt by a Alternator Shop.

I don't disagree at ALL, but sometimes people only have the choices they have. If there's a Denso available, that's would I would go with.
 
Joined
Dec 19, 2013
Messages
7,174
Location
Fort Worth, Texas
Haven't been too impressed with Denso Reman's either, If they can simply get away with throwing Brushes in, Repacking bearings, & Cleaning it up....That's exactly what they'll do.

Denso designs/manufactures really good alternators, But it's not to be confused with their remanufactured products.

This car will have either a Delco-Remy CS130 or a Delco-Remy 12SI, Denso likely sells a CS130....I just about guarantee it's bottom of the barrel junk from 3rd world supplier with a Denso sticker on it.
 

RAR

Joined
Mar 6, 2016
Messages
263
Location
Minnesota
Hi glorious and wonderous peoples of BITOG. : P I remain ever grateful for the people who share their knowledge and opinions...


I have a 91 chevy caprice classic, TBI 5.0L V8 which i assume needs an alternator. The only way that I know this is that in the middle of winter when it was 20 below I tried driving it and all the sudden the battery/charge light started flickering and lighting up... and that it's 31 years old/pretty sure the alt has never been replaced. I parked it for the moment (driving my 11mpg pickup instead not being up to a mid-winter wrench job) but finally got it out of a snowbank with rising temperatures literally yesterday. It had been started 2-3 times in jan/feb to see if it would keep the battery charged up - and it actually did, ran 20+ minutes fine (tho I wasn't watching the light, I just started and left it while shoveling snow to see if it'd die or live).

Now that it's out of the snowbank it did fine on two test drives around town for 30 miles in 20 degree temperatures, i'll doublecheck it at an O'rielly's or something but even if it passes the alt test I can think of no reason the battery/charge light would come on. (this has only idiot lights, no gauges so I can't watch for flickers or such) So I don't trust it. I'd rather wait until summer but I have to drive this out of town overnight so a breakdown would suck.

I assume the default answer will be just replace it, just wondering if anyone has any other advice. Like on amazon I see "other" small block chevy V8 alternators for cheaper than the ones they recommend, but maybe I should stick with those it recommends for my car... Amazon has AC Delco for $90ish, Rock Auto has some for a little less, i'm just curious if there's any caveats or "if youre changing X you might as well change Y at the same time" things. (not looking to do a waterpump, but a new serpentine belt probly makes sense/I don't remember when I last changed it)

I realize i'm asking some questions that might have obvious answers but i'm a TBI survivor and that's what it's like now, sorry if I need some handholding or walking through the process.
As others have mentioned, I would check and see if your belt and tensioner are working or are worn out.

A slipping belt and/or dying tensioner will cause the alternator to drop out and trigger that light on the dash. Run the car and watch if the belt is dancing around, or the tensioner is jumping around when running. Under load, it might be giving out and not spinning that alternator enough. And the power steering pump. And the water pump. So it’s worth looking at this simple check first.

If that’s OK, I’d put a volt meter on the battery terminals and the alternator terminal itself and check output when running. If that’s below 13.5 or so, I’d pull the OE alternator and find someone to rebuild. I’m assuming you’re near the metro area, so there should be a few options. Where I am, I am fortunate to have a guy here, and even a radiator shop (I was seeing this on another thread😎).

Do these first before ordering up an alternator. I know, since I replaced my failed OE starter on my Charger with a new TYC, and rebuilt the original with my local auto electric guy. That rebuild is back in, and the TYC was replaced under warranty after IT failed on me, and the replacement sits on my shelf. Good luck!
 

columnshift

Thread starter
Joined
Oct 6, 2014
Messages
251
Location
Minnesota
Just following up, I DID read by phone (but couldn't respond/forgot login), i'm deciding to go ahead and replace the alternator and belt. It was showing 12.9 volts while idling as soon as I turned the headlights on. Battery checked out good. Since the alt is 30 years old and where the vehicle is i'm NOT near somewhere I can rebuild it i'm ordering an online one but will keep the old one to possibly have rebuilt for the future. (actually does it matter which core i'd rebuild? Ie the original one that came with the car vs whatever I got online if that craps out later?)

I could save a few dollars doing other things, but since I have to travel out of town 100 miles from major cities the first tow charge would wipe that out. : P

Since people are panning newer AC Delco, any one have experience with or think this is any different?


as $30 less than (actually after shipping more like $5-19 less depending how fast i want it shipped), and claiming 'roadside tow/assistance' thing (who knows whats involved in claiming or proving that but whatever) vs


EDIT: Actually i'm probably just going amazon with the claimed new delco for simplicity after the shipping cost (esp cuz if it craps out it should be free return/replace), but i'm leaving up the thread just in case someone else is looking for similar information. : P
 
Last edited:
Top