90 alternator problem, I need some help with this one please.
Thread Starter
Le Mans Master
Joined: Oct 1999
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90 alternator problem, I need some help with this one please.
Long story short, Alternator died, put an old one I had laying around in (It was good when I had it on the car). It died 2 days later. I put another one in from Kragen (chain store) it is not charging. Went back and swapped it, new does not charge either.
Now I am worried there is something else wrong, but what?
The battery had 12 volts with engine off.
Start car and I have 11.5 volts.
Around the time the first alternator died my voltage gauge needle would bounce up and down a lot. I dont know if this indicates the problem I may have?
Any ideas where to start looking? What are the 3 wires that come out of the alt, I asume they deal with the regulator?
Where do they go?
I had the car running, disconected the negative battery cable and the car shut off.
I am lost on this one, unless the alt is bad, even though we tested it on a bench test and it puts out 13 volts.
:confused: :confused: :confused:
Now I am worried there is something else wrong, but what?
The battery had 12 volts with engine off.
Start car and I have 11.5 volts.
Around the time the first alternator died my voltage gauge needle would bounce up and down a lot. I dont know if this indicates the problem I may have?
Any ideas where to start looking? What are the 3 wires that come out of the alt, I asume they deal with the regulator?
Where do they go?
I had the car running, disconected the negative battery cable and the car shut off.
I am lost on this one, unless the alt is bad, even though we tested it on a bench test and it puts out 13 volts.
:confused: :confused: :confused:
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Re: 90 alternator problem, I need some help with this one please. (bill mcdonald)
The large red wire on the alternator goes to the battery and has a fusible link .
The fusible link is an in line fuse and I suspect since you know the alternator is good, then the in line fuse is open. Measure the voltage on the red wire to ground, it should be the same as the battery. If you read zero volts, then you will have to replace the fusible link. When you remove an alternator, you should remove the ground cable from the battery so that the wrench you use and the red wire you take off don't touch ground and blow the fusible link.
The fusible link is an in line fuse and I suspect since you know the alternator is good, then the in line fuse is open. Measure the voltage on the red wire to ground, it should be the same as the battery. If you read zero volts, then you will have to replace the fusible link. When you remove an alternator, you should remove the ground cable from the battery so that the wrench you use and the red wire you take off don't touch ground and blow the fusible link.
Thread Starter
Le Mans Master
Joined: Oct 1999
Posts: 6,366
Likes: 34
Re: 90 alternator problem, I need some help with this one please. (jfb)
Thanks for the reply.
With the car off, I have 12 volts, at the voltage terminal on the alt I have 6 volts... I guess I may have a short in the wire somewhere?
with the car on I found 11 V across the battery, and 3 volts at the alternator.
I learned about leaving the - wire connected to the battery and removing the alternators + wire the hard way long ago... I dont do that anymore.
With the car off, I have 12 volts, at the voltage terminal on the alt I have 6 volts... I guess I may have a short in the wire somewhere?
with the car on I found 11 V across the battery, and 3 volts at the alternator.
I learned about leaving the - wire connected to the battery and removing the alternators + wire the hard way long ago... I dont do that anymore.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: 90 alternator problem, I need some help with this one please. (bill mcdonald)
You have a blown fusible link in the alternator wire. Your voltmeter reads 6 volts because there is a high resistance (carbon) path in the blown link and your voltmeter is very high resistance. If you were to put a 12 volt light bulb from the red wire to ground it would not light because the blown link will pass only several microamps (millionths of an amp). Your voltmeter draws so little current to make a measurement that it will show some voltage. You will definetely remember changing that fusible link and for sure not change an alternator without disconnecting the battery ground first. Good luck.
Thread Starter
Le Mans Master
Joined: Oct 1999
Posts: 6,366
Likes: 34
Re: 90 alternator problem, I need some help with this one please. (jfb)
You will definetely remember changing that fusible link and for sure not change an alternator without disconnecting the battery ground first. Good luck.
Thanks for all the help
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: 90 alternator problem, I need some help with this one please. (bill mcdonald)
It isn't bad, but it will be a reminder to disconnect the battery.
Bill, put your head at the end of this sentence, thats right , right up against the screen :smash:
Bill, put your head at the end of this sentence, thats right , right up against the screen :smash:
