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2008 2.5 auto Alternator issues

2K views 2 replies 3 participants last post by  billymade 
#1 ·
OK so here is my problem:
Alternator bearing loud for a couple years, decide to replace because dash light occasionally came on and lights dimmed etc. Figured it was finally going out. Replaced easy. Start it up...light stays on. Meter and it's not charging.
B1 = 12.3V
P1 = 12.3V key off
= 9.1v key on
P2 = 0.30 key off
= 0.83 key on
Engine running is similar
Tracked 2 pin plug to 4 pin plug under battery.
Appeared to have 11.5v P1 and 11.2v P2 at source side of plug and the low numbers on alt side so... Splice magic and I have 11.5v and 11.2v key on now. Yaaaayy! Nope... Start engine and poof... P1 is 9.0v P2 is 0.80v, no charge etc etc.
I have tried direct jump to 12v and every suggestion for testing etc on all pins and Yada Yada. Lol
It almost seems like the ecm or? Once engine is started just decides... not today sir.
Battery is daily and tested good red top Optima with a 2nd good tested battery sitting next to it in case. Alternator is new, taken off and tested 14.5v. Got a 2nd new Alternator... Took to test taped up from manufacturer. Good to go 14.5v. All wires/connectors free of corrosion or cuts. Fuse link is good and no melting etc.
I am open like a 24 hour gas station for any ideas or blunt "this is your issue" helpful helps.😁
 
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#2 ·
Ok sitting in your driveway not running you battery should read with a multimeter at the battery terminals on a new/fully charged battery 12.6-12.8v, a somewhat used but still a good battery 12.4-12.5v, an old or somewhat discharged battery that is already giving you issues or will shortly, 12.1-12.3v.

With the car running you should be able with a multimeter to read at the same terminals on the battery 13.8-14.5v this indicates that your alternator is working properly. If you are not seeing that voltage at the battery terminals with the car running then you have a problem.

The first step would be to move the red multimeter wire to the bolt on the back of the alternator and see what the voltage is there, if it’s 13.8-14.5 the alternator is working but the proper voltage is not reaching the battery to keep it charged. That cold be from simply a loose or corroded connection or a bad cable.

If the alternator is not reading above 13.3.13.5 it will not keep up with the electrical demands of your vehicle. If you are getting the $100 parts store reman alternators you may have to go through 3 or 4 before you get a good one. Your best bet is to buy a new Bosch or a genuine Bosch reman.
 
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