Hi, I have a 1996 Chevy S10 Blazer, 4.3L 4x4. I have a 1200 watt amplifier with 2 10" Rockford Fosgate subs. I have the amp directly connected to my battery. Now i will explain my problem. So my stock, 105 amp alternator was bad. And it got worse little by little with my stereo. Everytime I put up my windows, locked and unlocked my doors, but on the headlights, the ac, windshield wipers, etc., the voltage needle on the gauges would move down a lot, and everything would dim. So I decided to finally buy a High Output Alternator on eBay. It is a 160 amp alternator. My mechanic installed it for me, and i also upgraded the positive cable to the alternator to a 4 gauge cable. Now, the problem has gotten a little worse. Now when i turn on everything at the same time-the headlights, the wipers, the rear wiper, rear defrost, ac, turn signals, raise or lower the windows, even turn the steering wheel, the needle goes really low, almost into the danger zone. I have noticed that my windows operate a lot slower than with the damaged, stock alternator. And today, the truck almost shut down on me. I contacted the guy from eBay that i bought the alternator from, and he said to measure the size of the pulley he gave me, and that he would send me a smaller one. The one that it has now measures 2.5 inches. He said he would send me a 1.9 inch pulley to solve the problem because supposedly, a smaller pulley will spin faster, creating more energy. And today i just took it to an auto electrician and he put a diagnostic machine on it. He told me that my high output alternator does not produce high output at idle, and he said that the problem was my 1200 watt amp. I really think this guy is wrong, why? I have a friend that has a 2000 Volkswagen Golf, and he has two amps of high wattage, and an in dash monitor. He still has his stock alternator and it is running perfectly. This is why i doubt that it is my sound system. Plus, i tested the problem on the truck with the system off. I turned on everything, the ac, headlights, etc. Except for the sound system. The truck still did the same thing. I was also told that a capacitor would help, but like i said, the sound system does drain a bit, but my friend told me that a simple turn signal should not cause a great drop in voltage. Someone please let me know if you think that the smaller pulley will solve my problem. This is a serious problem, because the truck is not performing to it's potential and it has almost shut down on me several times. Please give me any advice or ask me any questions that may help you find out the problem. Give me any tips or your opinions on what i should do or tell me what you believe the problem is. I would really appreciate it. Thanks, Rob.

 

a smaller pulley will help, but my guess is that wiring to amp is not big enough, what size are you running from amp to battery, and what size ground do you have. Itwould think those suspect, as my 2500 watts are running on a stock alternator and battery and I am having no problems. (just took out HO alt and yellow top because of sub recone)

 

Thanks for letting me know. I really don't know what size the wiring from the amp to the alternator is, because i did not do the installation. I will have to check on that. But thanks for telling me that the pulley will help. I appreciate it.
Rob

 

I would also check what the Alt is putting out at idle,Looking at what kind of amp you have, you might have a bigger problem. THat amp cannot be pulling that much power. Let me do some more research.

 

Another thing to check would be the battery.
How old is it?
Have it load tested.
The battery is the heart of your system, if you have a weak battery, you won't get the maximum out of your alternater.

 

I concur, have that thing tested.

 

I'll suggest the obvious... Unhook anything that you have added in and check all connections/wiring that were modified/tampered-with during your install of the various aftermarket equipment. Chances are that everything stock in the vehicle is working correctly and it is something that was added that is causing the problems.

Also, just upgrading the wire to the alternator alone isn't a good practice. The grounds from the battery to the chassis and the chassis to the engine block should also be upgraded to make sure that you are completing the loop. A simple faulty ground could also cause the issues you are experiencing.

 

I have had battery tested and it is workin perfectly. Matter of fact, it was just replaced a while ago. It is an AC Delco Professional Battery.

 

The guy that i bought the alternator from said this:

sir,

you have installed a custom high amp alternator it takes upgrades and a little extra work to get to work right some times. yes you should upgrade all cables and yes the pulley will make a huge difference. the high amp alternator does not run the same as your stock, it needs to maintain a higher rpm than your stock to function that is why you need the smaller pulley. this is all very normal, once you get it worked out correctly it will work great.


Do you guys think this will really work? I just need a few opinions to be sure.

 

Does a high output alternator require a pulley smaller than the one from your stock alternator to perform well?