Alternator/charging issues

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g0thiac

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I too have been having, charging issues with my Oldsmobile. I swapped the alternator with the one off the Pontiac, and upgraded the wiring. Tried different batteries.

I get 13.1v at the alternator with the stereo on and the lowest setting for heat too.

Grounds are new, so now I am sitting here trying to decide if theres a voltage drop. I have to jump start the vehicle, almost every time, especially when it's not warm man.
 

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ck80

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I too have been having, charging issues with my Oldsmobile. I swapped the alternator with the one off the Pontiac, and upgraded the wiring. Tried different batteries.

I get 13.1v at the alternator with the stereo on and the lowest setting for heat too.

Grounds are new, so now I am sitting here trying to decide if theres a voltage drop. I have to jump start the vehicle, almost every time, especially when it's not warm man.
But is it 13.1 with stereo, blower motor, everything else OFF?
 
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g0thiac

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But is it 13.1 with stereo, blower motor, everything else OFF?
I will check, but either way the amps of the stock alternator I do not trust on V belt GM vehicles also.
 

ck80

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I will check, but either way the amps of the stock alternator I do not trust on V belt GM vehicles also.
Point is, at idle each thing that's on drawing current can make an incremental voltage drop. And I don't think you had a small stereo IIRC.

At road speed, higher rpm, it's more likely to be a short drop and a climb back upwards, but idle speed? Especially on an older vehicle with some less than ideal grounds here and there and an older alternator? Not surprising.

Always test at the battery first with everything off except the engine itself. No blower motor. No defogger. No radio. No wipers. No lights internal or external. So on so forth. If you're seeing above 13 at idle with things drawing current you're probably OK. 13.5 is in the ideal zone. 13.1 is towards bare minimum. 12.9 is an issue.
 
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g0thiac

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Point is, at idle each thing that's on drawing current can make an incremental voltage drop. And I don't think you had a small stereo IIRC.

At road speed, higher rpm, it's more likely to be a short drop and a climb back upwards, but idle speed? Especially on an older vehicle with some less than ideal grounds here and there and an older alternator? Not surprising.

Always test at the battery first with everything off except the engine itself. No blower motor. No defogger. No radio. No wipers. No lights internal or external. So on so forth. If you're seeing above 13 at idle with things drawing current you're probably OK. 13.5 is in the ideal zone. 13.1 is towards bare minimum. 12.9 is an issue.
I agree, I will check with everything off but I think it's just old man.

And oh yes, the stereo now takes more power.

Well, it also did the same in the Pontiac during the winter so I am not surprised 🤷‍♀️🤣🤣🤣
 

ck80

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This is a brand new belt. Any ideas on what would cause this? View attachment 218012
Pictures are tough to diagnose. Here are my thoughts in no particular order that you can check out.

Could be either a loose pulley that wobbles due to bad bearing, a harmonic balancer issue, etc, where one of the grooves the belt passes over is wobbling. If the other belts are all OK, you can almost just narrow it down to an alternator pulley related issue.

test with different lengths of straight edges going from the face of the crank pulley to the faces of the other pulleys of something KNOWN to be square/straight. Think cheap wooden yard sticks or paint stir sticks on their edge, but not just a stick of lumber as theyre more known to be twisted.

check the grooves inside the pulleys that the belts pass through for rust, debris, etc. It should be clean and smooth, but sometimes isnt if it sat without a belt for a while

Jusy double check you have the correct width of belt for your pulleys, and, that someone didnt swap a pulley on - again, think old car and bubba just putting another gm alternator on from somethjng else. Although they're rare, a parts store salesman who is knowledgeable (sometimes NAPA) can help check that part.

Get a helper. Put them on the seat, you stand in FRONT of the engine, not to the side, and have them gently race and decellerate the engine while in park and watch for any flex or wobble in the pulley and brackets. Be careful in case a belt breaks, thats why you dont stand nest to, or look over the top, of the engine while trying this.

Could also be a bracket issue, or, someone hugged out /damaged where the bolt passes through so it sits cockeyed and out of square with the other pulleys, and, the stuck test should help with that. It'll show is its twisted out of alignment, or, if one pulley sits closet to the firewall than the other.

Could be again a pulley issue where a pulley is too tight on an alternator, then bearing is stiff and doesn't rotate at the same speed as the engine and the belt slips/skips as it passes over the binding (or even seizing) bearing, in which case you should see some smoke and burnt rubber effect where it's happening

Finally, double check, make sure to not over tighten the belt
 
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Street Sweeper22

Greasemonkey
Nov 18, 2017
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Pictures are tough to diagnose. Here are my thoughts in no particular order that you can check out.

Could be either a loose pulley that wobbles due to bad bearing, a harmonic balancer issue, etc, where one of the grooves the belt passes over is wobbling. If the other belts are all OK, you can almost just narrow it down to an alternator pulley related issue.

test with different lengths of straight edges going from the face of the crank pulley to the faces of the other pulleys of something KNOWN to be square/straight. Think cheap wooden yard sticks or paint stir sticks on their edge, but not just a stick of lumber as theyre more known to be twisted.

check the grooves inside the pulleys that the belts pass through for rust, debris, etc. It should be clean and smooth, but sometimes isnt if it sat without a belt for a while

Jusy double check you have the correct width of belt for your pulleys, and, that someone didnt swap a pulley on - again, think old car and bubba just putting another gm alternator on from somethjng else. Although they're rare, a parts store salesman who is knowledgeable (sometimes NAPA) can help check that part.

Get a helper. Put them on the seat, you stand in FRONT of the engine, not to the side, and have them gently race and decellerate the engine while in park and watch for any flex or wobble in the pulley and brackets. Be careful in case a belt breaks, thats why you dont stand nest to, or look over the top, of the engine while trying this.

Could also be a bracket issue, or, someone hugged out /damaged where the bolt passes through so it sits cockeyed and out of square with the other pulleys, and, the stuck test should help with that. It'll show is its twisted out of alignment, or, if one pulley sits closet to the firewall than the other.

Could be again a pulley issue where a pulley is too tight on an alternator, then bearing is stiff and doesn't rotate at the same speed as the engine and the belt slips/skips as it passes over the binding (or even seizing) bearing, in which case you should see some smoke and burnt rubber effect where it's happening

Finally, double check, make sure to not over tighten the belt
Yeah sorry about that pic. All the ridges on the inside of the belt are worn off. I’m on my way to get a new belt. The only thing that’s new is the alternator and battery. This is actually my 3rd alternator. All brand new in the box and I can’t figure it out. I’m going to do what you said and keep you posted. Thank you
 

Street Sweeper22

Greasemonkey
Nov 18, 2017
233
91
28
Yeah sorry about that pic. All the ridges on the inside of the belt are worn off. I’m on my way to get a new belt. The only thing that’s new is the alternator and battery. This is actually my 3rd alternator. All brand new in the box and I can’t figure it out. I’m going to do what you said and keep you posted. Thank you
It looks like my alternator wasn’t lined up with the water pump pulley so I got some washers and shimmed. So far it seems to doing good. When I’m driving it’s charging at 14.4v and when the fans kick on it drops to 14v.
 
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