alternator issues

xmas077

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98 continental
Bought new idler pulleys and alternator for my car to ellimimate some noises in the belt system. Old alt still worked but was noisy. Everything went fine with the installation.
Put everything back in and i started the car . After a few minutes of idling battterie light comes on in the dash and i noitice the voltage of the batt is going down. So my diduction is new alt. is not charging .

Steps i took to resovle the issue

Checked harness plug going to the alt.
Yellow/white wire is hot all the time .
Green/? wire is hot with key on.
Hotwired activation pin on alt. and still no charge . I think maybe the new alt. is bad.
Installed old alt. in the car and still have the same problem even though it work a hour earlier.
Rechecked harness plug with a test light still have good current .
Toke harness plug apart and pluged each wire in the alt.
Checked the fuse in the engine bay and it is fine. I don't know if there is one under the dash.

So now the new alt. will not not charge and the old alt. also does not charge. Batt. light is still on in the dash with both alts. and it comes off when when i disconnect the alt. when car is running. I'm lost.
 
A battery with a short can cause havoc with the alternator.
Has the battery been load tested to assure it is healthy?
 
A battery with a short can cause havoc with the alternator.
Has the battery been load tested to assure it is healthy?
New motorcraft batterie 2 months old.
Both batt. poll where disconnect during installation .
Worked great the day before.
 
A real bench test by an auto electrical shop or good independent mechanic can tell you the alternators condition, and if all the diodes are good and you have no AC voltage leaking that would create electrical problems. (I’m not a big fan of the chain auto stores)

It would not be the first time it took 2 or 3 “new” alternators to finally correct a charging problem.
 
I’ll have the new alt. tested tomorrow and I also bought a new harness alt. plug. The terminals seem loss and worn out.
Does someone know why the batt. light turns off in the dash if the alt. plug is unplugged while the car is running?
 
Looking at the wiring in the ’02 service manual –

The dash charge light is fed 12VDC on one side, and a LG/RD wire on the other side goes to the voltage regulator in the alternator - which (I assume) must ground the wire when the voltage is low. Disconnect this wire and the light goes out if it was on.
 
Got the new alt plug today. I replace the old one and bingo problem solved.
Thanks for the help.
 

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