Tech Question: alt not charging battery

[Earl_H]

This a follow-up to my earlier question...

Voltmeter falls from 10.5 to 0
Tach goes dead...


I replaced the alternator (new alternator tested before installed)
I tested the battery and I am seeing 12.5volts
AEM is reading 10.5 volts

My car is a twin turbo with an AEM PCM.

Any suggestions? If not, anyone know of a competent tech in Michigan?

 

[Earl_H]

Found out battery was bad...replaced it, but it didn't fix the problem. By the way, before I replaced the battery, after replacing the alt., the AEM and the voltmeter read 12.5V. Turned off the car and the problem came back.

 

[Earl_H]

bump

 

[KepRght]

that rebuilt alternator is suspect to me, take it to a different rebuilder and have them test it,.

i have had 3 dead ((NEW)) batteries before back to back. all dead. and seen several re-built alternators that "test" ok but get them home and dont put out.

also tripple check all of your wiring, make sure everything is seated correctly & not corroded.

when you said

"By the way, before I replaced the battery, after replacing the alt., the AEM and the voltmeter read 12.5V. Turned off the car and the problem came back"

this sounds like the new battery supplied juice for a bit (the 12.5V) and then when it wore out from not getting a charge from the bum alternator, the issue returned. my finger is pointed at a bum new alternator, or bad wiring to/from the alternator. its eating your batteries.

hope that helps.