I got an 02 Z28. when i go to work in the morning the lights are flickering. my amp guage shows about 14 to 15. when i leave in the afternoon the amp guage is at 12 and if it idels it slowly drops to the red. while im going down the road it goes up but the needle jumps around. So is it the alternator going bad? and the lights why are they flashing when its showing good voltage? im confused.

 

The gage you are looking at is not an amp gage (ammeter) but a voltmeter. The low voltage could due due to a bad connection, bad cable, sick alternator, or bad battery. Being that the lights are flickering, and the voltmeter bouncing, it may just be a bad connection or a bad cable. Clean battery terminals & tighten, check ground connections, check cables between battery & alternator, clean cable terminals and check for corrosion under insulation and make sure the connection between terminal and cable is tight (wiggle test).

 

I had the same condition on my SS a few years back, and an alternator replacement solved it. While you're at it, see if your battery is good -- a bad battery can create alternator problems too...

There is a big long thread on alternators on LS1tech, and the stock alts suck at idle voltage, regardless...

 

you probably have a bad connection ive had a bad altenator before and you know when its your altenator because you will only run as long as your battery last because your altenator isnt charging your battery so therefor you probably wouldnt be able to crank your car after you drove it in the morning if that makes any sense.

 

I went to a shop and they told me my alternator was going bad. I got a 160 amp alternator off ebay. I just put it in today, took forever. That thing was a pain in the butt to get off. But its still droping volts at idle. but if i turn the ac off it quits. Any ideas now?

 

Get a cheap slide on ammeter $20, place it over one of the battery cables, (12V or ground, does not matter). Check cutrrent draw when engine is running with fans OFF and then with fans ON. The fans should draw less than an additional 40 AMP. If the fand are drawing excessive current, change them out. If the draw is within range, make sure the small wire to the alternator shows battery voltage. If not, the alternator is not seeng the proper control voltage and will not develop full power.

 

i would guess the a/c clutch is goin and drawing a mess of amps. could be the fans as well, they come on with the a/c, the wires to either should be checked to.

 

look for loose or corroded terminals on your battery, if you have a hand held digital multi meter you should do a battery load test and measure the voltage of the battery with the car off and on, with the car off a healthy battery should be about 12.2-12.5 volts, with the car running and no accy's on Ie. a/c,radio,headlights etc. the voltage should be approx 14.4 volts, to do a battery load test you need to disconnect the neg terminal and set your meter to measure AMP's and possibly change your probe locations on the meter, and connect the meter in between the neg cable and the neg bat terminal. this measurement should be as low as possible .3mA and lower (only do this with car off!).