So I never really realized this until today, but when my passenger window goes up by itself, it works fine. If I do 2 windows at once, the driver side and passenger, it goes up slower, which I always noticed but figured it was just a weakened motor. It worked so I never questioned it. Well I put in new speakers() and realized when I cranked them, my lights dim. It is not a dim where it goes dim and then comes back to normal, it stays dim, even if I have the radio off and close the windows, it dims. I am assuming my alternator is not strong enough to power everything all at once, and was wondering how much head room I have on a stock alternator with a stock truck. I thought I had about 10 amps, so I figured speakers with a small amp would be no problem, but I only just realized that my alternator can not even power the truck stock. I figured it wasn't the regulator, because I will run the truck at 2000RPM, and the problem persists, where the lights stay dimmed.

Basically, how much power does the truck need stock? I believe the stock alternator is 130Amps, and I was thinking about kicking it up to 200 Amps if the need arises. How much would a 200A alternator cost me, I have seen them for ~$300-400, which seems about right. Also, I was thinking about getting an isolator, so can anyone find me one online that is rated for 200A or 220A. 220A would be preferable because I would rather have a little head room and not run the thing at what it was made for, thus why I am getting a 200A alternator, even if I only use 140Amps. I plan on adding a few more batteries also, thats why I need the isolator. I also plan on doing the big 3 upgrade. Has anyone done this, and what gauge wire is sufficient? I heard like 0 gauge, but want to be sure.

Thanks for the help FTE!

 

The power output of the stock alternator is not the problem. The fact that the lights go dim and stay that way even after you turn the radio off is a sign of another problem. If you were being limited by the alternator output, the lights would return to normal brightness once the radio was turned back off.

 

Maybe I worded it wrong, let me try to re-explain. The lights go dim if I turn the radio on, and go normal when its off. They go dim when i roll down the windows, but go back to normal when i stop moving the windows. The passenger window slows down if I roll down the driver side window, but rolls down normal speed when it alone is being rolled down. Thanks for the fast response.

 

Check your battery cables for corrosion or looseness. You're not getting full power to your accessories and it has nothing to do with the alternator (assuming it's working properly.)