I ahve an 01' with the 3.8 v6. The battery died about a month ago so i took it to Auto Zone and had them put in a new one. Last week I started getting voltage drops and it acted like it was gonna die so I took it to the dealership and they said it was the alternator so they replaced it. The car was fine for a day then it started doing it all over again.

I have an aftermarket stereo system I installed myself 2 years ago and never had a problem with it, they are saying that I probably need a bigger alternator to run the amps, but I unhooked the power wire running to the trunk so its not drawing anything from the battery and the problems still persists. the check engine light is now on and when you are driving it if you pull the headlight switch out to turn the headlights off it quits with the jerky driving and acting like its going to stall.

The voltage meter is all over the place too... its been running really low then it'll shoot back up and come back down and all the lights dim and flicker as well.

Auto Zone put in a bigger battery (replaced a 650 with an 875 amp). Is it possible that the new alternator cant supply enough juice to the new battery or is it possible that the dealership put in a smaller alternator? The new alternator got tested at Auto Zone and they said it was putting out 80 amps...the stock Alty was 136 amp.

Any ideas what causing this problem? I've had it to the chevy dealership three times in the last week and they keep saying there isnt a problem or if there is a problem its the stereo equipment Ive put in. Im taking it to an auto electrical specialty shop on wednesday but any insight would help.

 

they told me the same thing when mine was actiong up the min they find a stereo amp wire and a fuse they assume it is the issue. Im not pulling 3000 wats out of the car im lucky for 1000 total in the whole stereo LOL
but i have a optima bat in my car now. and also i have upgraded the ground wires on the alt. starter and the chassi grounds.

Also clean the connections real well put them back then use a bat. term sealer to spray over them so it will help seal them from coroding again.

I dont know what it is about monte carlos but they are real finikey about ground wires. and if they dont have a good contact they will not run .

Also have the dealer ship check your guages on the dash this all could be due to a bad bord in the dash.

or of course the sun could be to brite where you live and it has cused the light sensor to start acting up and causes the lights to flicker on and off LOL
(what my dealer told me was wrong with my dash lights)

 

Since it is a new alternator I would have it checked again. They don't make a 80 amp for the Monte. I think the smallest is the 130.

I would check to make sure the backup jump connectors are fine too. They are on the black box about a foot up the fender.