my elctrical headaches
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Senior User
Joined: Aug 2009
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ok so i went and got the original alt checked out at advanced auto and it tested fun. so i dont think the problem is battery or alternator. what else is in the loop. is there a regulator or fuse somehwere?
Mountain Pass
Joined: Oct 2007
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If you have only 12.3 volts when running at the battery, and the alternator is working then you have a bad connection between B+ on the alternator and the battery. Measure at B+ on the alternator. If you have 12.3 there, then there is still something wrong with the alternator or regulator. I don't know on your year where the regulator is but on later models it is part of the alternator.
Post Fiend
Joined: Jul 2005
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Mountain Pass
Joined: Oct 2007
Posts: 185
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You'll have to look at how it's routed. It's the big wire and it does get back to the positive of the battery. It may go to the starter first and then directly to the battery, or most likely it goes directly to the battery. But, make the voltage measurement first. A volt meter is a valuable tool - you need to use it instead of shotgunning things!
FTE Leadership Emeritus
Joined: Jul 2002
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From: Long Island USA
The big wire from the alternator goes to the starter relay/solenoid on the inner fender near the battery, I think.
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Senior User
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So I took volt meter and was checking continuity. If I go from b+ on alt to either pos or neg of battery meter beeps. Short? I think I found regulater....some corosion on it...... need to check starter too
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Post Fiend
Joined: Jul 2005
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Very simple.
Remove the regulator from inside the casing.
Then, simply place in this testing machine:
Next, place it in this container:
Now, if the regulator somehow made its way back to your alternator on its own, it test good.
If it stays in the can, it test bad.
Unless you have the equipment --- high priced electronics testers ---- you are much better off to throw out what is a $5 part.
Good regulators at retail sell for a pittance.
Why bother?
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Senior User
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So I get the same voltage at the b+ pn alt as I do at battery. It looks like the thick alt wire goes to atarter solenoid then to battery. Can I hook it straight to battery. Shld I be getting a higher voltage if I put voltmeter on b+ alt with truck running
FTE Leadership Emeritus
Joined: Jul 2002
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From: Long Island USA
But I don't think that's your problem.
Either there's something wrong with the alternator, or the sense wire to the alt is disconnected.
If you look at the schematic below, it's for a 2001, but should be the same for your 1999.
The "fusible link c" provides sense voltage to the regulator so it can monitor battery voltage.
HOWEVER, if you notice, it says something about "with voltage applied to the I circuit" which I take to mean that the battery light HAS TO BE THERE.
When you first turn the key to ON, without starting the engine, does the battery light come on?
Post Fiend
Joined: Jul 2005
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The key-
The "I" circuit cannot have "full power", but has to be loaded with a resistor and the Battery light.
It is an exciter for the rectifier --- without about 8 to 9V there (not more) the alternator does nothing.
I still say it is a pigtail problem.