I have an 01 blazer 4wd, 2door. For the last year my voltage is drooping a lot. I assumed my alternator was on its last leg. If you turn the blower motor on for AC you can watch it droop or when you put the turn signals on you can watch it droop. I replaced the alternator last week and it is still doing the same thing. I have verified that the gauge in the vehicle is correct with a handheld multimeter. I have checked and cleaned my battery cables and it is still doing it. I went to Advance this morning and they ran it thru a fairly complete test and battery voltage is 12.7 V resting , load test good. 200A draw/ load test good while engine is on. After the truck is off, there is a 600mA draw on the battery. This seems way to high to me. I should note that after a month of sitting the truck will still start up but is a little weak. After its run a while it fires right up very strong with no indication of a weak battery or anything.

1) I believe the parasitic draw should be about 40 mA for this truck after 5 minutes.

2)what is the draw before it goes into shutdown mode? Is .6A normal?

3) Im thinking this may be a bad ground issue.

I will check the parasitic draw tonight for a few minutes to see if the .6A changes to something lower.

 

id check the voltage somewhere in the cab, like from the fuse box if possible. i have a 90 fullsize that has a funky gauge. like you said it drops down with the a/c turn signals and everything else. when im running full blast a/c headlights and everything it says im charging at about 11v but the multimeter tells me 13. stupid gauge

 

While monitoring the draw, start pulling fuses until the draw stops. Im not sure what the parasitic should be, but at least you could find it. 600 ma does seem high to me also.