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New Battery New Alternator Lights still flicker

I have a 2008 Saturn Vue , in summer of 2018 the vehicle started to have flickering lights, ac turn off and on etc and was becoming hard to turn on. Took only a day for it to shut down while driving. I pulled to the side and it never came back on. We realized the alternator ate up the battery since we couldnt jump it. Took it to pepboys since they could replace the alternator quick.

So new batt and alternator. Yet ever since, I will accelerate and my battery light will come on , the dash lights flicker and headlights as well. The more i change in speed specifically accelerate or even go up hill, the more the car seems to loose charge? Everything flickers . But once I sustain a steady speed it does not, and eventually lights stop flickering.
I have taken it back to pepboys a couple times they said they could never find the problem ( once the cars stopped and parked for a few minutes the battery light goes away like nothing happened) and that its a wire issue and they can’t fix that. Also everytime we check charge on batt and alt , its pushing out -perfect everytime.
What can it be ? Ive already spent $1000 for the new batt alternator and labor.

Most time its due to a loose battery cable.Make sure they are tight.

Loose or dirty battery cables check both cables both ends.
Bad cables.
Bad, dirty or loose alternator belt.

If you are checking the alternators output I assume you are using a multi meter while it is running and comparing the voltage to when it is off ?

If that checks out ok…then it could simply be the connection that handles the charge light, it may be loose in its connector on the alternator. However, that doesn’t explain the dash flicker…The flickering dash lights can be caused by a faulty dash light dimmer switch, which is common…move the dimmer up and down and be sure it seems stable and doesn’t induce flicker.

Another source of the electrical gremlin is where the fuse box gets its power feed…be sure that is tight and not faulty. Alternator connection needs to be clean and tight…batt terminals of course as well.

I would do the multi meter test…and also have an assistant move the plug on the alternator (engine running) while someone looks at the dash…if the alternator light flickers with someone playing with the plug…then it is just the charge indicator light/plug or a wire broken near that plug.

Just some things to check

This vehicle has some age to it, so it may just be a weak serpentine belt tensioner.

Yosemite