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Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 16899
Experience:  15 years GM master tech
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Replaced altenator in 99 S 10 twice, first new one was bad

Customer Question

Replaced altenator in 99 S 10 twice, first new one was bad as well. Not charging. Battery was disconected both times prior to removal/installation.
Submitted: 2 years ago.
Category: Chevy
Expert:  Gary replied 2 years ago.
Welcome! My name is ***** ***** I will do my best to assist you with this problem.Ask me about added features such as phone contact anytime if you wish !
I am sorry for the long wait
is this a 4 or a 6 cylinder engine ?
do you have a multi meter on hand ?
Customer: replied 2 years ago.

Multimeter is broken. 6 cylinder, voltage meter in gauge cluster is reading 10.5. Last new alternator had a bad regulator, I had them test this one before I left and it was good. I'm guessing there's a relay or fuseable link in this

pig somewhere.

Expert:  Gary replied 2 years ago.
there should be a big red wire bolted to the alternator stud does that stud show 12 volts at it ?
then there is only one small wire in the alternator connector correct ?
Customer: replied 2 years ago.

Can't tell without a meter and, it only has the one big red wire, no other plugs or wires.

This alternator has a built in voltage regulator.

Expert:  Gary replied 2 years ago.
on a 1999 it HAS to have a big electrical plug plugged into it with one small red wire
is it just not plugged in ?
it has an internal voltage regulator in it but that regulator is turned on and off and how much to charge from that red wire from the computer
Customer: replied 2 years ago.

The outlet for a large plug is in the alternator but there is not plug from the truck for it, I'll go double check. If there was it hasn't ever been plugged in since I've owned this truck.

Expert:  Gary replied 2 years ago.
see if its there but the 1999 truck had a plug and the computer controlled the charging
it is the only way the alternator can charge unless someone installed the wrong alternator originally and didnt need it plugged in but any stock 1999 has to have a plug
Customer: replied 2 years ago.

Well, it's not quite stock. 383 Stroker, built by a mechanical engineer on Robby Gordon's Nascar team. Has Accell GenVII on board ECM with Fuel injection. Used stock S10 alternator for past nine years with just the power wire and worked fine until Alternator went out.

Expert:  Gary replied 2 years ago.

it would have been nice to know this right off the bat that this was not stock and modified and you told me 6 cylinder when it has a V8

is the alternator you replaced the same part number of the original one ? if so then we have to know if the big stud shows 12 volts at it next

Customer: replied 2 years ago.

It has been replaced with identical alternator. I'll have to go buy new meter.

Expert:  Gary replied 2 years ago.
so the odds are the alternator is a self charging alternator and if you replaced it and tested good then the odds are that big power wire is missing 12 volts
if so that power wire connects to the passenger side lower inside radiator support off a 175 amp fuse mounted there see if that big fuse shows 12 volts on both sides of it
Customer: replied 2 years ago.

Will do but again, I have to get a meter, it will be later on. Any chance we re-connect?

Expert:  Gary replied 2 years ago.
sure thing just replay right back through this post for any follow up