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Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 15435
Experience:  15 years GM master tech
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Chevrolet S10: My 2003 s10 headlights and dash lights flicker

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My 2003 s10 headlights and dash lights flicker at night or when I hit the brakes at night sometimes. It is so intermittent that I think it is some main ground return that is loose, but not sure which wires to check in harness.
Welcome to Justanswer ! my name is XXXXX XXXXX i will do my best to assist you with this problem
im sorry your having this problem
how long has this been doing this ?
how long have you owned the truck ?
did this start out of the blue one day ?
Customer: replied 3 years ago.

I would say for about 5 of the 10 years that I owned the vehicle it will sometimes do this.


Owned the S10 since 2003 when I bought it.


Yeah, this started out of the blue.


Thanks for replying, because I definitely don't want to spend $300 for the dealer level maintenance manual just to see the wiring diagrams because that is just crazy. So, what do you think it could be? You have access to the dealer level maintenance manual that you could photo copy and put up?




yes i do
but first we have to start with some basics you need to remove and clean both battery cables on the battery
then follow the negative cable to the engine and make sure it is clean and tight
then follow off the negative battery cable the smaller ground off of the negative battery cable and make sure that is clean and tight where it connects to the body
Customer: replied 3 years ago.

Checked and found all of them good. Even the wire braid ground that goes from the engine to the firewall is good.

ok good job
at this point you more than likely have a bad alternator causing this BUT can you make a ground wire and attach it to the alternator case with one end and then the other end to a good ground and see if it still does this ?
Customer: replied 3 years ago.

I got some 1 AWG welding cable and the terminal lugs that the alternator mounting bolt can fit through and the fire wall bolt ground screw can fit through. I'll give that a try. Have to head to work and at nighttime I will know if this fixes the flicker issue. Will be back tomorrow after 3rd shift is over.

no problem i will reply back as soon as i can be patient
Customer: replied 3 years ago.

Well, I believe it is the alternator. I hooked up my Fluke 289 to the alternator output and ran very long probe wires from outside hood through my door seal and then to meter. When I uploaded the voltage graph log onto my computer, I could see an almost 3 volt dip on the graphed data. These dips coincided with my lights all dimming at those events of voltage drop.


In case I want to rebuild the alternator, could give me the AC Delco part numbers for the internals, except for the stator and rotor? If I see that the rotor slip rings in my alternator have grooves or if I see insulation damage to rotor or stator, then I will just replace the whole alternator with OEM. Thanks for the help.

here cut and paste this Auto Zone should have what you need

its very rare we take them apart with the price or a remanufactured complete alternator V/S the rebuild parts

Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 15435
Experience: 15 years GM master tech
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