another charging issue - Ford Mustang Forums : Mustang Forum
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post #1 of 5 Old 01-21-2012, 09:42 PM Thread Starter
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another charging issue

i have a problem that baffles me beyond belief
.i have an 89gt (original motor) i have udp's and a 3g volts at idle fluctuate and vary from 14.5- 13.7 with nothing on.with lights on 13...with heater 12.2 or so.sometimes its low that i cant even play my radio at idle.
also some days when i start it volts are steady at 14.5 and my guage reads a hair above half way.i can turn on my lights and the guage will drop to a hair or more under halfway.when i turn the lights back off...sometimes the gauge doesnt move back to above midway...almost like it doesnt recover
another strange thing to me is that some days my volts will flucuate like i have a lopey idle...but my idle isnt flucuating at the time the volts are.
i have double checked all my 3g alt wiring.not using the original fusible black and orange wires.have 4g power and ground wires.

ive been told my udp are to blame and a over drive pulley on the alt would fix this.
reasons for this belief is- for one when i have no volts i can barely put my foot on the gas...not even enough to see the rpms volts go back up...the second is because i dont have this issue driving.while driving i can run everything and the guage stays a hair under halfway...

sorry for being so long...hope i didnt leave anything out.any insight would be appreciated as this is my first mustang.

*forgot to add that the ground from the back of the motor to the firewall is attached and from battery to block is new.

Last edited by n4arush; 01-21-2012 at 10:15 PM.
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post #2 of 5 Old 01-22-2012, 12:03 AM Thread Starter
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over 20 views and not a single person has any insight,thoughts...anything? think the over drive pulley will fix my issue?

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post #3 of 5 Old 02-11-2012, 08:50 AM
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dump the UD pullies.

a 10G alt will not even help, when you underspin it.

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #4 of 5 Old 02-11-2012, 03:47 PM
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Most alts will show higher voltage when they are cold. As they warm up they become less efficient and will output less voltage.

Fix the pulleys and make sure the alt is grounded to the block well.

Another thing to note is that your car can still run to about 10-11v... not sure why yours wont. Seems to be a bigger issue i think than just the alt.
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post #5 of 5 Old 02-12-2012, 02:22 PM
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check all your grounds also do a voltage drop test on individual circuits to make sure all your wire is good also it could be a matter of installing a relay or 2
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