1993 Mercury Sable Alternator

Tiny
MOBES_01
  • MEMBER
  • 1993 MERCURY SABLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 200,000 MILES
I can not get the alternator to charge the battery. Have in stalled a new battery and three new Alternators for it keeps burning them up. Every time I test the battery with the enigine off its at 12 volts. When running it begings to fall. Testing off the Alternator it says.24 volts. Have replaced all the connectors to the alternator and still nothing. Now I have all the wires pulled out and looking for a short and I cant find one. I found some corrosion in a plug that runs from group of wire down to the oxgen sensor, but I dont see how that even connects into the alternator. I hate electrical work and my brain is about to explod!
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Monday, August 9th, 2010 AT 4:15 PM

3 Replies

Tiny
CARADIODOC
  • EXPERT
Hi mobes_01. Welcome to the forum. Where are you finding this.24 volts? Also, describe the connector. Do you have the regulator built onto the back with a green / red wire and a yellow wire with a fat one bolted to the rear or do you have one with the plug on the side with two really fat black wires with orange stripes in the plug itself?

Caradiodoc
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Monday, August 9th, 2010 AT 5:56 PM
Tiny
MOBES_01
  • MEMBER
It has the regulator built on the side of the alternator. I got the.24 from the main positive post a black and orange wire going to it. I also got a connection with a yellow and white, green and red, and a white one. Then a third connection of a blue wire.
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Friday, August 13th, 2010 AT 2:06 PM
Tiny
CARADIODOC
  • EXPERT
Now the question is where was the other meter probe? If you measured.24 volts from the output wire to ground, suspect a blown fuse or corroded connector. The output wire must have full battery voltage all the time. If a very large fuse is blown and the generator is working, you will measure a much higher voltage when the engine is running, typically around 15 - 18 volts because it's not getting back to the battery which would help regulate it.

If you're measuring between the output wire and the battery positive post while the engine is running, ideally there should be 0 volts difference, but no wires are ideal; they all have some resistance, and the.24 volts would be the result of current flowing through that resistance.

You can also measure the voltage on the white wire while the engine is running. If it has around 6 - 8 volts, the generator is producing output. That voltage is what tells the regulator to raise the voltage on the green / red wire to turn off the warning light on the dash.

Caradiodoc
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Friday, August 13th, 2010 AT 2:29 PM

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