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04ctd · 06-21-2012, 09:15 AM

14.4 is what it SHOULD be at the Alt while running.

now...if you have 13.3 with no load, you have a bad Alt.

and ALWAYS move your ground to three different locations to verify you have a good ground.
I have worked on two cars lately for a few hours before I figured out the ground was bad (had multimeter on Batt Ground terminal)
once I put the ground lead for the meter on the frame, i had +7v everywhere

so put the ground on the:
-battery
-engine (carries ground for alternator, usually)
-firewall (lots of electronics ground there)
and see how it all measures. that will SAVE alot of time...ask me how i know...

so test Volts at Alt,
-idling (rev it up first, some alternators need to go above a certian RPM to "self excite")
-revved up (say ~2500 RPPM)
-Idling loaded (lights, AC, radio)
-revved up loaded.

then, do all the same tests at your battery.

it sounds like the Alt is weak, because even with an UD pulley, at 2500 RPM it should make the juice.

if your voltage varies greatly (the Alt & battery readings) from the front of the car to the rear, then you have a bad connection somewhere.

all you guys should read this when you are bored next time, lot of info here:
http://www.madelectrical.com/electri...witworks.shtml

The on board charging system must exceed the 12.6 level for electrical current to flow through the battery during charging. Electrical current must flow through the battery during charging to cause chemical reaction between the liquid acid and the lead plates within the battery. The 14.2volt level causes about the correct amount of current flow through the battery to maintain a fully charged condition.

06-21-2012, 09:15 AM	#18
04ctd Senior Member Join Date: Aug 2009 Location: Ladson SC Posts: 4,388	14.4 is what it SHOULD be at the Alt while running. now...if you have 13.3 with no load, you have a bad Alt. and ALWAYS move your ground to three different locations to verify you have a good ground. I have worked on two cars lately for a few hours before I figured out the ground was bad (had multimeter on Batt Ground terminal) once I put the ground lead for the meter on the frame, i had +7v everywhere so put the ground on the: -battery -engine (carries ground for alternator, usually) -firewall (lots of electronics ground there) and see how it all measures. that will SAVE alot of time...ask me how i know... so test Volts at Alt, -idling (rev it up first, some alternators need to go above a certian RPM to "self excite") -revved up (say ~2500 RPPM) -Idling loaded (lights, AC, radio) -revved up loaded. then, do all the same tests at your battery. it sounds like the Alt is weak, because even with an UD pulley, at 2500 RPM it should make the juice. if your voltage varies greatly (the Alt & battery readings) from the front of the car to the rear, then you have a bad connection somewhere. all you guys should read this when you are bored next time, lot of info here: http://www.madelectrical.com/electri...witworks.shtml The on board charging system must exceed the 12.6 level for electrical current to flow through the battery during charging. Electrical current must flow through the battery during charging to cause chemical reaction between the liquid acid and the lead plates within the battery. The 14.2volt level causes about the correct amount of current flow through the battery to maintain a fully charged condition. __________________ 1 Timothy 3:16 16 And without controversy great is the mystery of godliness: God was manifested in the flesh, Justified in the Spirit, Seen by angels, Preached among the Gentiles, Believed on in the world, Received up in glory. Last edited by 04ctd; 06-21-2012 at 09:18 AM.