alternator issues

[cinz4064]

i recently installed a underdrive crank pully in my mark viii now the alternator isn't charging at an idle that pully is still stock do i need a bigger or smaller pully for the alternator
also if i change the idle whats the max rpm i can set it to without messing anything up

 

[racecougar]

A smaller alternator pulley would speed the alternator up.

 

[LaserSVT]

As for max RPM, you can go as high as you want just dont expect the brakes to last. 1000 rpm is about as high as I would set one but still wouldnt like it that high.

Thats why I hate underdrives........ come to think of it my white Mark I had to put an underdrive crank on it and the only time it had charging issues was at summer, AC on MAX and headlights on with brakes on and sitting still for over 5 minutes like in a drive through.

Your alt may be weak.

 

[blacklsc1]

underdrives suck. i have them on my mark 8 and i installed a 200 amp alternator cause i knew i was gonna have a problem, but it just doesent spin fast enough at idle(450) to charge. im gonna get a tune to bump the idle up to 700 and that should take care of it. on the plus side i did feel a bump in power.

 

[ford nut]

Your alt may be weak.

Bingo.
These cars need 14v or they have fits.
Go back to stock pulley, check at batt what your pulling for amps.
If it is not over 14v you will have issues.

 

[danny_holtermann]

http://www.lincolnvscadillac.com/showthread.php?t=76473

This thread should help you out