Mechanics

NEW ALTERNATOR AND NEW BATTERY. THE ALTERNATORIS NOT CHARGING THE BATTERY.

1997 Mercury Sable • 170,000 miles

I have a 1997 Mercury Sable and the low voltage light came on. I checked the voltage on the battery and sure enough the battery was not charging. I removed the alternator and had it checked, dead, so I replaced the alternator and the battery. The low voltage light went out but the alternator is not charging the battery. The voltage before start is 12.7 and after I start the car the battery voltage drops to 12.3. I have checked the wires for corrosion and shorts but I see nothing wrong. I checked the voltage coming out of the alternator at the terminal point (wire with bolt) and it is showing 12.3. Any ideas?
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Oldhamd
August 28, 2011.




With the key on, any voltage at the I terminal at multiwire connector? I looked at info for a motorcraft generator.
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JDL
Aug 28, 2011.
Charging system wiring, below.


JDL
Aug 28, 2011.
Started car and no voltage on the I terminal


Tiny
Oldhamd
Aug 28, 2011.
There may be a problem with indicator lite or wiring. The info shows a resistor to bypass the lite incase the lite-bulb vibrates out socket, or goes out. Does the charge lite on the dash work?

I've seen diagrams like this before, with the bypass, generator would not charge unless lite was fixed.


JDL
Aug 28, 2011.
The light does not come on. It came on originally when I had low voltage on the bad alternator. I replaced the alternator and the light went out. I assumed it was because I fixed the problem. According to the owners manual the light should come on briefly when the key is turned to the on position. It does not! Is there a fuse I should be looking for to replace?


Tiny
Oldhamd
Aug 28, 2011.
The fuse is in the diagram, goes hot/voltage with key on. If fuse is ok, use voltage tester at fuse leg, where the fuse plugs in.


JDL
Aug 28, 2011.
You are the man! Replaced the fuse and alternator is charging the battery to 14.25 v

Thanks a lot.


Tiny
Oldhamd
Aug 28, 2011.
Glad you got it going your way. Hope the fuse doesn't blow again? Maybe it was the old generator that caused it to blow?


JDL
Aug 28, 2011.

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