Alternator problems?

[Guardsman]

The following has been happening. Normally, my voltmeter is reading about 14/15 volts. Occasionally, when I hit the brakes, the voltage drops to about 12/13 volts, then when I hit the gas again, it goes back up to 14/15 volts. When the voltage drops, then comes back up, it drops right to 12/13 volts, then goes right back up to 14/15 volts, it doesn't waver around or anything. It almost seems like it's doing it on purpose. Any ideas? Thanks.

[vtv6firebird]

My car has done the same thing since I bought it in '97. I would say it is just the way the car is, even if annoying when at night the lights dim when you slow down and step on the brakes. I have had three alternators, each differnt brands and the car responded the same way with each one installed. It is most likely due to the alternator not being able to supply charge at low RPM's. Even higher amperage alternators cant supply much current at 700 rpm's.

[Guardsman]

Cool, thanks.

[Skullcamaro]

Same here. I have a high amp alternator and I still sometimes get that drop when I stop for a period of time at a red light. One thing to remember when you upgrade your alternator or electrical system is the gauge wire you use, it can make a big difference. Check some car magazines like car craft or hotrod or Gm high tech performance. They have had articles listing the gauge of wire you should use for the type/amp alternator you use.

[Skullcamaro]

One thing that may help this problem, regardless of whether or not you have a high amp alternator is the gauge of wire that is being used to connect the alternator and battery, grounds, etc. I suggest going to a lower gauge wire such as a 2 gauge or 0 gauge wire to supply more power directly.

[bu-bye]

another quick add to wires if I may.... Having a wire with more fibers will give you a better connection. Elect flows around the outside of each strand so if you have more strands the power will flow better. If you just have one big wire rod its wont be as good. Go to a Stereo shop and look at the wires you will see that the better wires have a lot more tiny strands and the copper looks cleaner. In the stereo world wires make a HUGE difference, for your Alt I don't think it matters but I thought I would lay it out it anyway.

[ July 10, 2002: Message edited by: bu-bye ]</p>

[Skullcamaro]

I'm just curious as to how effective a lower gauge wire would be such as a 0,1,2 gauge wire on your battery cable/alternator cables. I have a problem with my voltage dropping at idle when I have my a/c on whether it be with my headlights or not. I have a 140 amp alternator that puts out at least 80-90 amps at idle. I shouldn't be having any problems. But I saw an article that stated that a lower gauge wire would increase the effectiveness of the output and increase the power available. I have both underdrive pullies on at the moment but it doesn't seem to matter if I do or don't, except that the voltage meter goes down a little lower and my abs inop light comes on to save power but everything is fine when I accelerate and nothing is wrong with the belt or wires, spark plugs, etc. Any suggestions would be helpfull. I understand your point about stereo equiptment and multi fiber wires but a lower gauge wire allows more current to flow easier then a higher gauge and is recommened in a high amp environment.

[Guardsman]

I'm pretty sure that the problem is that the regulator is shot, it's been happening more frequently, and I'm starting to get fluctuations occasioanally when I put the windows down at idle, etc. I've located another alternator (there's no rebuild kit out yet, just remanned alternators), and I'm going to try that.
SkullCamaro, the voltage drop doesn't have anything to do with the size wire that you're running, it's because the alternator isn't keeping up with the load on the system. I don't know if the regulators on these alternators are just slow, or just pieces of junk. The main thing that determines the size wire is primarily the current load on the system.
Larger wire will help a bit with better electrical flow, but unless you're going to a really high-output stereo system or using something that requires precise voltage and current levels, I don't think that you would notice that much of a difference. Where the size of the wire is really important is, again, the current load, because of the heat generated. If the wire isn't big enough, you run the risk of burning things up, and possibly a fire.
The thing to keep in mind concerning our vehicles is that GM is going to use the absolute minimum size wire that can handle the anticipated load, for cost and weight reasons. Our stock alternator is rated for 105 amps, but if GM figures that the typical max load that will be on the system is only 80 or 90 amps, then they will install wire that is only rated to handle 80 or 90 amps.
If you're going to re-wire for, say, your stereo, then you would need to increase the size of the power wires to the stereo, amp, etc., and also check the size of the wires feeding the power distribution block, and increase those, if necessary. That would involve many enjoyable ( :rolleyes: ) hours of tracing wires through the harnesses, disassembling the harnesses, rewiring them, etc., etc., etc. And, in the end, you'd still be limited by the power input pins at the equipment.
If your pins are made for 18 gauge wire, and you're going to 16,12, or whatever gauge wire, you're stuck, and if your load is really enough to justify increasing the size of your wiring, then you're looking at the possibility of serious problems down the road by runnig 12 gauge wire through the harness, and then splicing that to a 18 gauge input pin.

[Skullcamaro]

The reason I was going to lower the gauge of the battery and alternator wires was because I have a high amp alternator now installed. It hasn't mattered which altnernator type I've used the result of low voltage at idle has been typical for quite a while now even without the undrive pullies. Thier was some report done in a magazine about the different gauge wiring being used and it said that the higher the amp and depending on distance of the wire then the different type of gauge wires matters a lot. I'm not sure what the stock gauge wire is but lowering it to either 2, 1, or 0 gauge would definantly improve the flow of the voltage being processed.

[Guardsman]

The output of your alternator doesn't matter when you want to determine what size wire you want to use. The actual load that you put on your system is what will determine it.
The length of the wire becomes an issue because as the wire gets longer, the resistance gets higher. Again, the issue is heat. Using a lower gauge wire is not as much for the lower resistance, which is minor in the lengths we're talking about for your car, it's more for the heat dissipation. Look at the load that you have on your system now, and what you realisitically expect in the future, and use that to determine the size wire to run. If you have the time and money, and want to play it safe, run the size wire necessary to handle 140 amps. There are charts around that show what size wire you should use for what size loads, you should be able to find them on the internet.