camaroman101

iTrader: (1)

okay so i just bought my first LS and im already having some problems. The previous owner installed a set of underdrive pulleys both crank and a smaller alternator pulley. It charges fine when not using any accessories but even when using the headlights they dim and the battery voltage gauge will drop. I hate having to constantly keep an eye on the battery gauge. would a 145a truck alternator do the trick? buy a set of stock pulleys? Bump up the idle? Its an a4 with a cheatr cam and idles at 550 rpm in drive. thanks for any advice

ULTIMATEORANGESS

iTrader: (4)

a4 cars might require an idle adjustment to maintain a correct charge.

farmington

iTrader: (14)

a smaller alternator pulley would make the alternator turn faster, not slower

ULTIMATEORANGESS

iTrader: (4)

a couple questions if i may.

while what you say is correct wouldnt a crank pulley still cause more drag and drain on an a4 car even with an alternator pulley?

ive always thought autos didnt benefit from an alt pulley? i dont have one on my car.

camaroman101

iTrader: (1)

I thought autos were supposed to used the alt pulley as we have a lower idle rpm. Should i be worried about breaking the timing chain with the ud pulley or is that just for guys who road race? its an slp pulley

ULTIMATEORANGESS

iTrader: (4)

SLP which is the same as a power bond i believe is a quality part.


as long as its properly installed i wouldnt worry about anything breaking.

LFSADRG

iTrader: (1)

Same situation on my stock LS1 after I installed the UDP. Added 100 rpm at idle which helped out.

01ssreda4

iTrader: (96)

Yes, autos idle at 550 in gear. By reducing that with an UD pulley the alt will have a hard time keeping up under high load situations like AC and lights. OP, does a blip of the throttle make your voltage jump to normal? If it does you may just need the smaller alt pulley that returns it to normal speed. Due to the heavy AC use here in the south I went with the alt pulley right from the beginning and have not had any issues. WS6store has the pulley and belt you will need.

99Bluz28

iTrader: (35)

I'd recommend having the idle speed raised up at least 100rpm, since many alternators have a fairly low output at low rpm.

99T/AMAN

iTrader: (1)

What are you guys considering as low output? What is the gauge reading? My car has been having problems with holding a charge and the voltage gauge only reads 13v when running and will go a little below sometimes also. Rpm does not seem to make mine any better either. I have UD crank pulley also. I am wondering if my alternator is starting to go bad

Tuskyz28

My buddy had the same issue. He took off the f body alternator and bought one for a escalade and issue was fixed. I guess the escalade alternator puts out more power than the f body alternator do.

01ssreda4

iTrader: (96)

You cannot diagnose an alternator through a stock gauge. A battery is 2.1v per cell, 6 cells total for a normal voltage of 12.6 approx. Anything above this indicates a charge state. That means at 12.8v the alternator IS technically charging but there are some norms in the automotive world to follow. Generally speaking with no load on the electrical system (AC, lights, stereo off) you generally see a voltage of 13.5 to 14.5. When you load the system down with everything on, I like it to maintain 12.9 or higher but some systems can maintain mid 13s loaded. I've never seen a 14 as loaded voltage, and have never seen a 12 on unloaded voltage on systems that were functioning properly.

zhero21

iTrader: (3)

with 550rpm I would definitely raise the idle