Alternator bad? Follow my trial and error. Am I wrong?
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Joined: Feb 2001
Posts: 8,494
Likes: 411
From: Sophia, NC
Car: 2016 Camaro SS + 1986 Z28
Alternator bad? Follow my trial and error. Am I wrong?
Alternator bad? Follow my trial and error. Am I wrong?
First off, I have done the three upgrade a few years ago, and I recently went through and checked all my connections.
So I've been having on and off no start/low batteries. Been checking the charge both running and off, and while running, I'm seeing low volts, which would indicate something to do with the alternator. Sometimes as high as 13.5, which is low, or sometimes as low as 12.2, (bad) and maybe lower, but I'm essentially reading whatever the battery has left in it at that point.
I took the alt to the shop that painted it and rebuilt it for me, and they said it checked out fine, and I'm probably seeing low volts because the "2" wire (the brown with white) might have a short, a blown fuse, or something that's messing with the internal voltage reg. OK cool, that makes sense.
With the car off, I read 12.25 (a little low from all the trial and error). At the alt. 12.25. At the red always hot, I read 12.25, and 0 at the brown/white. flip the key on and it now reads 12.25 exactly as it should. I start the car, alt reads 13.5, and after a real quick spin around the block, it reads 12.2. Shut it off, and same thing, every checks out perfect. (except the fact that obviously the battery's a tad low.
Am I right to thing this is an alternator/volt reg. issue, and NOT my car's electronics? It would almost be a no brainer, but they told me it checked out fine. ....gonna call 'em back Monday, but I'm tempted to go the carquest and get a reman and see what happens.
First off, I have done the three upgrade a few years ago, and I recently went through and checked all my connections.
So I've been having on and off no start/low batteries. Been checking the charge both running and off, and while running, I'm seeing low volts, which would indicate something to do with the alternator. Sometimes as high as 13.5, which is low, or sometimes as low as 12.2, (bad) and maybe lower, but I'm essentially reading whatever the battery has left in it at that point.
I took the alt to the shop that painted it and rebuilt it for me, and they said it checked out fine, and I'm probably seeing low volts because the "2" wire (the brown with white) might have a short, a blown fuse, or something that's messing with the internal voltage reg. OK cool, that makes sense.
With the car off, I read 12.25 (a little low from all the trial and error). At the alt. 12.25. At the red always hot, I read 12.25, and 0 at the brown/white. flip the key on and it now reads 12.25 exactly as it should. I start the car, alt reads 13.5, and after a real quick spin around the block, it reads 12.2. Shut it off, and same thing, every checks out perfect. (except the fact that obviously the battery's a tad low.
Am I right to thing this is an alternator/volt reg. issue, and NOT my car's electronics? It would almost be a no brainer, but they told me it checked out fine. ....gonna call 'em back Monday, but I'm tempted to go the carquest and get a reman and see what happens.
Joined: Nov 2007
Posts: 845
Likes: 4
From: Salt Lake
Car: 1989 IROC & ROLL-Z
Engine: L98 Vortec FIRST TPI
Transmission: T56, Mech Speedo
Axle/Gears: G92 J65 3.27
Re: Alternator bad? Follow my trial and error. Am I wrong?
What caused you to start checking into all this? Battery died? Dim lights?
know what I mean? Like what is the "real world" problem?
Couple of cars we've had over the years have had charging issues. Take the alternator to autozone or what ever to check it out and they say its working fine.
Yet get them to warranty the alternator and put a new one in, voila, battery stops going dead.
know what I mean? Like what is the "real world" problem?
Couple of cars we've had over the years have had charging issues. Take the alternator to autozone or what ever to check it out and they say its working fine.
Yet get them to warranty the alternator and put a new one in, voila, battery stops going dead.
Thread Starter
Joined: Feb 2001
Posts: 8,494
Likes: 411
From: Sophia, NC
Car: 2016 Camaro SS + 1986 Z28
Re: Alternator bad? Follow my trial and error. Am I wrong?
Real world? -car wouldn't start! LOL....
....and I agree with you. I've heard several stories about the Advance/Zone type stores, but I went to an auto electric place, and I've heard they run it through a few more tests. Whatever. I don't know. Gonna get a new alt and see what happens.
....and I agree with you. I've heard several stories about the Advance/Zone type stores, but I went to an auto electric place, and I've heard they run it through a few more tests. Whatever. I don't know. Gonna get a new alt and see what happens.
Joined: Sep 2005
Posts: 27,893
Likes: 2,435
Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
Re: Alternator bad? Follow my trial and error. Am I wrong?
When you turn the key on w engine not running, does the "Alt" light come on?
If not, change the bulb.
If not, change the bulb.
Member
Joined: Jun 2014
Posts: 180
Likes: 0
From: Chantilly, VA
Car: 88 Chimera
Engine: 1994 LO5 5.7L
Transmission: 700R4
Axle/Gears: 2.73...?
Re: Alternator bad? Follow my trial and error. Am I wrong?
I've never seen my ALT light on my panel (not sure if my Fbird has one).
Did have a deal alternator though. Battery gauge never moved when the car fired up. Eventually it read around 8v and couldnt power the injectors anymore... and died. In town.
New alternator and it fired right to to 13.5v on the dash. Battery sits around 10-12.
Still no light
My alternator cost me 25$ from the junkyard. Got it from an S10 blazer.
Works great.
Thread Starter
Joined: Feb 2001
Posts: 8,494
Likes: 411
From: Sophia, NC
Car: 2016 Camaro SS + 1986 Z28
Re: Alternator bad? Follow my trial and error. Am I wrong?
Yeah, If I have an alt. light, I've never noticed. ...the volts on the dash do sit low, around 8 or 9, and like I've said, I've checked the alternator pigtail over and over. Red is always hot, brown/white (when switch is on) is always the same as the battery.
Joined: Nov 2007
Posts: 845
Likes: 4
From: Salt Lake
Car: 1989 IROC & ROLL-Z
Engine: L98 Vortec FIRST TPI
Transmission: T56, Mech Speedo
Axle/Gears: G92 J65 3.27
Re: Alternator bad? Follow my trial and error. Am I wrong?
On my 89' the battery light is on the left side of the steering column.
Comes on along with the service engine light when I turn the key to on every time.
Comes on along with the service engine light when I turn the key to on every time.
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Re: Alternator bad? Follow my trial and error. Am I wrong?
Some random observations and questions:
Since the alternator will operate at 13.5V under some conditions, it might seem to be intact. However, thermal and electrical stress on the alternator can affect its output. I have experienced cases where the rotor wires at the slip rings become resistive, brittle, and loose, and fail to make adequate contact once the alternator reaches temperature.
Similarly, the slip rings and brushes need to be inspected for signs of resistive heating or sticking. Thermal breakdown of the diodes in the rectifier bridge is not a common problem, but in a case like this the connections, insulation washers, and ground connection of the bridge should be verified. The regulator module itself can suffer from thermal breakdown and resistive connections, so inspection is also advisable.
The other major component of the system is the battery. Does it maintain voltage (even low voltage) after being disconnected? Even a weakly charged battery should either maintain or actually recover voltage after disconnection. A partially shorted, sulphated, failing battery will tend to lose voltage.
Quite simply, if you have another alternator, it may be easiest to install it and test drive the vehicle to evaluate the problem.
- At 12.2V charging, the battery will never get fully charged.
- Is your analytical voltmeter accurate? Don't rely upon the meter in the instrument panel.
- Did the bench test of the alternator include a load test for 20 minutes? if not, the alternator may have never reached operating temperature.
- It would seem from your reported results that the brown/white exciter at the alternator is always the same as the measured battery voltage. Is that correct? If so, the wiring and ignition switch are probably not a problem.
Since the alternator will operate at 13.5V under some conditions, it might seem to be intact. However, thermal and electrical stress on the alternator can affect its output. I have experienced cases where the rotor wires at the slip rings become resistive, brittle, and loose, and fail to make adequate contact once the alternator reaches temperature.
Similarly, the slip rings and brushes need to be inspected for signs of resistive heating or sticking. Thermal breakdown of the diodes in the rectifier bridge is not a common problem, but in a case like this the connections, insulation washers, and ground connection of the bridge should be verified. The regulator module itself can suffer from thermal breakdown and resistive connections, so inspection is also advisable.
The other major component of the system is the battery. Does it maintain voltage (even low voltage) after being disconnected? Even a weakly charged battery should either maintain or actually recover voltage after disconnection. A partially shorted, sulphated, failing battery will tend to lose voltage.
Quite simply, if you have another alternator, it may be easiest to install it and test drive the vehicle to evaluate the problem.
Banned
Joined: Nov 2008
Posts: 2,435
Likes: 1
From: Central Florida
Car: 89 Camaro RS running MS2X
Engine: .48/.60AR T3/T4 2.8L V6
Transmission: Rebuilt 700R4 2500 stall
Axle/Gears: Next to break...
Some random observations and questions:[*]At 12.2V charging, the battery will never get fully charged.[*]Is your analytical voltmeter accurate? Don't rely upon the meter in the instrument panel.[*]Did the bench test of the alternator include a load test for 20 minutes? if not, the alternator may have never reached operating temperature.[*]It would seem from your reported results that the brown/white exciter at the alternator is always the same as the measured battery voltage. Is that correct? If so, the wiring and ignition switch are probably not a problem.
Since the alternator will operate at 13.5V under some conditions, it might seem to be intact. However, thermal and electrical stress on the alternator can affect its output. I have experienced cases where the rotor wires at the slip rings become resistive, brittle, and loose, and fail to make adequate contact once the alternator reaches temperature.
Similarly, the slip rings and brushes need to be inspected for signs of resistive heating or sticking. Thermal breakdown of the diodes in the rectifier bridge is not a common problem, but in a case like this the connections, insulation washers, and ground connection of the bridge should be verified. The regulator module itself can suffer from thermal breakdown and resistive connections, so inspection is also advisable.
The other major component of the system is the battery. Does it maintain voltage (even low voltage) after being disconnected? Even a weakly charged battery should either maintain or actually recover voltage after disconnection. A partially shorted, sulphated, failing battery will tend to lose voltage.
Quite simply, if you have another alternator, it may be easiest to install it and test drive the vehicle to evaluate the problem.
Since the alternator will operate at 13.5V under some conditions, it might seem to be intact. However, thermal and electrical stress on the alternator can affect its output. I have experienced cases where the rotor wires at the slip rings become resistive, brittle, and loose, and fail to make adequate contact once the alternator reaches temperature.
Similarly, the slip rings and brushes need to be inspected for signs of resistive heating or sticking. Thermal breakdown of the diodes in the rectifier bridge is not a common problem, but in a case like this the connections, insulation washers, and ground connection of the bridge should be verified. The regulator module itself can suffer from thermal breakdown and resistive connections, so inspection is also advisable.
The other major component of the system is the battery. Does it maintain voltage (even low voltage) after being disconnected? Even a weakly charged battery should either maintain or actually recover voltage after disconnection. A partially shorted, sulphated, failing battery will tend to lose voltage.
Quite simply, if you have another alternator, it may be easiest to install it and test drive the vehicle to evaluate the problem.
If the battery doesnt have good capacity from dead cells, then it will almost always read low. Just a thought.
Meant to quote the OP. My bad
Thread Starter
Joined: Feb 2001
Posts: 8,494
Likes: 411
From: Sophia, NC
Car: 2016 Camaro SS + 1986 Z28
Re: Alternator bad? Follow my trial and error. Am I wrong?
At 12.2V charging, the battery will never get fully charged.
Is your analytical voltmeter accurate? Don't rely upon the meter in the instrument panel.
It would seem from your reported results that the brown/white exciter at the alternator is always the same as the measured battery voltage. Is that correct? If so, the wiring and ignition switch are probably not a problem.
Did the bench test of the alternator include a load test for 20 minutes? if not, the alternator may have never reached operating temperature.
Thanks for the replies everyone. I don't think I'm gonna "test" much more, just gonna get a new alternator and see what's up. I actually came to that conclusion two weeks ago, but when I brought it by the Auto Electric place for a rebuild, they said it was ok, and kinda through me thought process off. ...and only reason I didn't go right to the parts store is because it's paint matched and clocked at 12/6 for my aftermarket brackets.
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