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2004 ZR2 Blazer w/Headlights & Dash Lights Flickering

I will start out with a little history of the situation. A little over three months ago my original altenator died with over 200,000 miles on it. I took it in and had it replaced (they used a refurbished altenator) and about a 1-1/2 months later is when the issue started. The headlights and dash lights will flicker and whenever they dim, the volt guage will go down. When the lights come back to normal brightness the volt guage will also go back to normal. All this will go on for random lengths of time as I am driving. I took the vehicle back to where I had the altenator replaced and they replaced it again under warranty. About another 1-1/2 months went by and the same thing started happening. I took it back to the same garage and this time they put in a brand new altenator. Finally about a week after this last visit to the garage the symptoms came back. Does anyone have any idea of what could be causing this? Thanks ahead of time for the help.

This is usually due to a bonding strap between the engine and the body. I’m not sure why this strap would be removed for an alternator replacement, but it might just be corrosion where it is attached.

Another place to look would be the ground connection for the alternator. Pull out the mounting bolts, clean the areas that the mounting bolts contact, both on the engine and on the alternator, and on the bolts themselves.

Last thing is the battery terminals must be clean, free of corrosion and tight. Check the ground (-) cable at both ends.

Well just the other day I had it into a garage for some unrelated maintence and told them about this. They checked all the grounds and said they all looked go. I have been asking people that I know about this and I have heard a bunch of different possibilities. Anything from a ground being loose to the alternator manufacturer getting a bad batch of regulators to there being a wire that is causing a draw on the system. This issue is getting very frustrating so any help would be greatly appreciated.

The first thing you need to do is properly test your battery. If it’s over 5 years old, replace it now.
The basis for anything electrical in a car is a battery in proper operating condition. Over the years I’ve run into poor charging conditions which were CAUSED by bad batteries.