Every time I flip on the AC or roll down the windows, my voltage drops to 10 volts or a little lower. I have a new Alternator in the car and the Optima battery in it is 2 years old I believe. The previous owner put it in. I recently had it charged and it still does the same thing. What is causing this draw? I want to fix it because the car stalled at a light one time with the AC on. I have to turn it off while at idle. If I'm driving it takes a few minutes for it to go back up to 13 volts. Any ideas? Thanks.

ttt

I have the same problem with my '87 Iroc. When I have the ac on the voltage drops when I'm at a stop and have the brake down. When I take off the voltage goes up again. When I'm making a turn with the ac on, and have to put the brake to slow down, voltage drops and then goes up as I accelerate. Also, I have to put the ac on heater for it to stop. It's annoying, or when I have the lights and ac or radio at the same time the voltage also drops. The alternator works and I have a new battery too. Could it be some kind of short. Any info will appreciated. Thanks.

sounds like bad grounds

Yeah, check main grounds

Battery to Head/block (behind AC pump)
Battery to Chassi (small cable)
Block/Head to Chassi (firewall)

I changed my main powercables out some days ago.
BIG difference. I went with 2 AWG from battery -> Starter and 2 AWG from Battery -> Block/head

Also changed out the alternator wire to an 7 AWG.

Charging is at a constand 14.54volt now. not moving when putting load on the engine.
So old cables can make "problems" so have your grounds and main power cable checked out.

Thanks for the info. Can I get pics of where the main grounds are that you just described? Thanks.

Thanks for the info guys really appreciate it.

Got some pictures (the 2 last posts) from my main power cable change in this thread:
http://www.thirdgen.org/techboard/el...e-battery.html (New Power Cable (battery->Starter))

Also I will attach 1 picture on the main ground on the head here (saw that I missed to attach it on the thread above)

Old wire behind the AC pump (passengerside).


New Main Ground intalled:


Check the linked thread for more info about the change

Thanks

I just ordered these 1/0 guage battery and power cables from Gary. It was a nice install. Now with these installed, the car voltage stays at a steady 13 volts while driving and at idle. However, once I hit the AC switch, the voltage drops back down to near 8 volts and my turn signals start flashing really slow. What is causing this? Seems like I'm back at square one again. My main ground was on the passenger side of my 87 in front of the smog pump, which is different than yours since you have an 89. Is there anything else I'm missing that I overlooked?

could be a shorted coil in the A/C compressor clutch?

Could it be the block head to chasis/firewall ground? Where is it located on the 87 IROC? It's a 350.

Meaning Ac compressor would need to be replaced? How much do those things cost if a shop were to do it?

I took it to a shop the other day to have it inspected for the issues I was experiencing. They however saw that my alternator was not charging like it should. This is the 2nd time I replaced a 105 amp alternator from advanced auto in 6 months. I'm wondering if a 140 amp will help or is that overkill? Ac compressor tested good as well. I however need to get a bracket for the rear of the AC compressor which is missing. Does anyone have one on hand they don't need?

140 AMP alternator would work. You cant go to big there

But I would start searching for the real reason they break for you instead. maybe you have some bad connections or something that makes them go bad. are your car overheating ? is it cooling the engine correctly ?

I read through this quick but experienced something similar. I was thinking all along it might be the alternator barely providing enough and then the voltage dropping when accessories were turned on. I drove a couple of days before replacing the alternator on mine and haven't had any problems since.

Anyways, it's not uncommon for aftermarket alternators to fail. I had a lifetime warranty on one for a different car that I replaced 4-5 times before selling it. If you have someplace local that can rebuild them for you then I would go that route. That way you know what you are getting and have someone to bring it back to in case it fails again.

I agree that other things should be checked out in case they are causing the issue as that is the only thing that will ultimately resolve the issue in such cases. But I've seen the alts go out too often to rule them out.

The car doesn't overheat at all. No problems there. All my connections look good. I replaced the 3 major cables for battery,starter, alternator from innovative wiring.

I see what you are saying. The only problem I have with getting a 140amp alternator is the fact that they only carry them in chrome at the auto advanced store. The other thing is that they only provide a one year replacement warranty on it compared to lifetime warranty for a "worldwide" brand alternator at 105amps. Where would be a good source online to buy a 140amp alternator that is not in chrome?

I would try finding a local place that will rebuild them. There's at least two here in the Twin Cities in MN, there has to be someone local where you are.

Good posts. Was looking for the same info.

I have the same problem right now....

Ok so when I got my 86 IROC-Z with a 305 TPI, and I knew the alternator wasnt keeping up with the needs of the Camaro. I wanted to get a better alternator, better than stock. Stock amp is 105-108. I was looking for something a bit better. The stock alternator case is the GM 12csi or -12. But the only ones I found were on Summit Racing are 145amp, but they are chrome, and not wanting chrome I just wanted a better output than oem. So I went with a oem figuring it should do just fine. I got a oem alt from the parts store (autozone / O'Reilys), but they were all clocked wrong on the case. As the back of the case need to be clocked or turn to the right to use the factory spacer on the bottom of the alt that bolts to the back of the case. Well after that issue I have a new alt in it and with the lights on and the a/c going and in gear the volt gauge drops to the bottom. But with lights on and in gear its fine. With the lights off and the a/c on, no problem. So my question is has anyone else run into this problem? Where the alt cant keep up with the car? I would assume that a oem style alt should keep up with the needs of the car. I know that the new alt is doing fine, with the car running and in park or in gear it shows just fine at the 13 mark on the gauge. But if I have both the lights and a/c or have any other draw it just drops to the bottom......

hopefully that wasnt to confusing...... This might sound the same thing as above, but I have posted this on a few different forums to see what kind of response I can get..

have you guys checked your serpentine belt or v-belts, are they streched or is your your automatic tensioner getting weak?

also if youre going off of your volt meter gauge, how is that circuit?....my iroc is always at 13v or a bit under, then the other day on my way to work i noticed the gauge was between 8 and 13v and fluctuating, i pullied it into the shop when i got to work and checked it with my multi meter while the gauge was at 11ishv my dmm was reading a steady 14.45v. and have checked on it several times since and 14.4v everytime.

on my 90rs i use a 650cca napa gold battery and a 140 amp napa gold alternator that will carge at a steady 14v with lights on, a/c on, radiator fan running,pinoneer sterio powerng a 800 watt amp pushing two 10inch subs on a 100 degree day.

and i almost always find my self replacing new new or almost autozone,kragen,o'rielly alternators at work with oem alts almost every three days, and whn i do side work i always recommend oem new or reman alts.

I am having the same issues, I have a Duralast Gold coming from Autozone tomorrow. If it doesn't work I will try the napa gold Alt. This will be the 3rd one from them.

So I have driven it for a while now and it doesn't seem to be as bad as before. The new alt is in and working, I do know that the gauge isnt in the best shape, if I tap on it when its low (below the 13 mark) it will wiggle back. But if I am driving at night with the lights on and the a/c running, when the a/c kicks on it will drop a bit, but will come back up. So I am looking for a new factory volt meter gauge. Someone also told me to check out some of the fusable links (like around the starter) that are in part to the grounds and make sure that they are all good. I have checked the grounds and they all look fine, for the ones I can see, I have not got a chance to get under it and check there and all the connections. The one goal is to have this '86 IROC-Z run like it was brand new and have that volt gauge steady at 13, and have not draw or pull on it. Also this is all orginal car, no aftermarket, no stereo besides the orginal.

Thanks for the reply, The Alt seems to be doing the trick. I also replaced the signal flasher with an electric one and that cured my other issue.