Ok, my factory alternator always used to be just below the 13 volt mark but when I used my brakes my light would dim just for sec, so I bought a 160amp alternator. Everything was going great but the P.O.S. only lasted for 500 miles before breaking!

Then I bought a regular replacement alternator. Now when ever I have my A/C on and I use my brakes at a light, my friggin volts drop to like 8!!!! They of course go back up when the revves go back up but WTF??? When I don't use my A/C it only goes down just past the 13 volt mark with just the brakes, or if I am not using A/C and I have all of my lights on, it will still drop but not so far.

Is there a power vampire in my A/C???? Or what? The voltage in my 91 NEVER moves, everthing is perfect and my 92 used to be the same but iwas always kinds low at just a hair below 13.

 

What shape is the battery in? Before attempting any alternator replacement start with a fully charged battery. How much output does the replacement alt have? The higher the amperage of the alternator the less it has at idle. A 160 amp alt will generate little or no output at anything less the 1000rpm's. In some cases with an idiot light it will start to flicker with a high output unit. It is pretty normal in the summer heat as the battery efficiency goes down to see a large voltage drop with AC, cooling fans and blower motor running. At idle, you are drawing more current than the alternator is putting out. As always, check cables grounds yada yada yada. Another thing to consider is that the aftermarket units being sold by the chains are less that ideal quality. You might want to consider an AC Delco replacement. They seem to have better quality control than most of the junk being sold.

 

Thanks, I kinda figured most of that. The battery is a new AC Delco (new like 4 months new) and the alternator is the 105 amp I believe. The wire to the battery was replaced with an EXACT replacement if not better.

I'm talking about voltage going from like 14 volts to like 8. I know it's most likely because my car idles so low from the SLP chip plus the A/C on and the over 110 degrees of summer but damn. Is there anything I can do or do I just live with it?

Alex

 

I have an 89 iroc, all stock with exception of zz-4 block. AC Delco batt, 105 amp alt. With the 100+ temps here in eastern PA with all the crap running I dip pretty low too. If you spend most of your time idleing it might drain the battery a little, but as soon as you get moving it will recharge it pretty quick. If you want more soup at idle just get a smaller pulley. Check out www.alternatorparts.com. They carry all sorts of stuff for charging systems. Dan