1995 Ford Windstar alternator

Tiny
MARKLONGBERRY@HUGHES.NET
  • MEMBER
  • 1995 FORD WINDSTAR
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
I'VE JUST WENT THROUGH 5 NEW ALTERNATORS TRYING TO GET MY SYSTEM TO CHARGE. HAS A NEW BOSCH BATTERY AND ALL THE ALTERNATORS IVE PURCHASED SEEM TO SELF DESTRUCT. I THINK THE REGULATORS SENT WITH THESE REMANUFACTURED ALTS. HAS SOMETHING TO DO WITH THE PROBLEM. CAN U HLP/?

THE BELT TENSION IS GOOD, WIRING LOOKS GOOD, GROUNDS LOOK GOOD. WON'T CHRG. KILLS ALTS?
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Sunday, November 7th, 2010 AT 5:07 PM

6 Replies

Tiny
CARADIODOC
  • EXPERT
In what way do they self-destruct? Does your generator have a rectangular plug on the side with two large black wires with orange stripes?

Caradiodoc
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Sunday, November 7th, 2010 AT 5:24 PM
Tiny
MARKLONGBERRY@HUGHES.NET
  • MEMBER
The altern. In question has a lrg. Blk.+Orng. Wire running from the fuze box to the B+ term. @ The regulator which is housed on the backside of the alt. There are also a 3way conn. Plus a single wire to the dash. All conn. @ The reg. The reg. Is a small white rectalinnear devise.
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Sunday, November 7th, 2010 AT 8:17 PM
Tiny
MARKLONGBERRY@HUGHES.NET
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They test fine at the store but die the second they are installed. Wires look fine no loose conn. Cant find a short. Battery is brand new, and dies a little ways down the road.
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Sunday, November 7th, 2010 AT 8:26 PM
Tiny
CARADIODOC
  • EXPERT
Do you mean they simply don't work when installed, I hope? There really isn't anything in the vehicle that can destroy a generator, and by their very nature, they are self-regulating as far as current is concerned. They simply will not produce significantly more current than they are designed for.

First, does the battery light turn on as soon as you turn on the ignition switch? If so, that circuit is ok. It is the "turn-on" signal for the voltage regulator. You should also find around 2.0 volts on the green wire in the regulator plug when the light is on. Once the system is working, there will be near full battery voltage on that wire and that voltage will turn the light off.

Next, there must be full battery voltage on the yellow wire all the time. That is the main power source for the regulator and it is the wire the regulator uses to sense system voltage. If that voltage is missing, look for a blown 15 amp fuse.

There must also be full battery voltage on that fat black / orange wire all the time. If that one is missing, look for a blown very large bolted-in fuse. It could have been blown by the previous generator but more likely that wire touched ground and arced, especially if you didn't disconnect the battery while doing the replacement.

You won't find any voltage on the white wire at first, but when the generator is working, there will be near half of full battery voltage on that wire. It's that voltage that tells the regulator to raise the voltage on the green wire to turn the light off.

There are two ways to tell if the system is working. Look for around 6 volts on the white wire, or measure battery voltage while the engine is running. The voltage must be between 13.75 and 14.75 volts. Besides identifying a no-charge condition, the regulator will also turn the warning light on in the event of an over-charge condition.

Caradiodoc
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Sunday, November 7th, 2010 AT 9:49 PM
Tiny
MARKLONGBERRY@HUGHES.NET
  • MEMBER
To Cardiodoc,
the batt. Light comes on, and approx 2.4 volts at that term. Still doesn't explain dead alts. I have reciepts on hand of the last four i've installed that went by-by. Iv'e put alts. In my other vehcls. No prob. What gives? Also I took the blk. Orng. Wire loose @ fuse box to check volts from b+ term. To box, read 35 volts on b+ term. This reading from 2 separate alts. At one time this vehcle. Had a loose grnd. @ Starter and result was heater motor and lights would stay on? Again these alts tested good on leaving the store, after a half hour of driving they are dead. Batt. Is new w 800+ cc amps new alts.
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Monday, November 8th, 2010 AT 9:44 AM
Tiny
CARADIODOC
  • EXPERT
Did you measure the voltage on the yellow wire? You should not be disconnecting the output wire when the engine is running. The battery is a key part of regulating system voltage. 35 volts will exceed the reverse limits of the generator's internal diodes and one of them can short. That will lead to overheating of the other ones. As a general rule of thumb, when one diode is shorted, you will only be able to get very nearly one third of the generator's rated capacity. A 90 amp generator will only produce 30 amps which is sufficient for most driving conditions, but there will be excessive ripple that can interfere with some computers on the vehicle.

If you are getting no output at all when the units fail, look at the regulator on the back of one of them. You will see it is held on with four screws in a rectangular pattern, and there are two additional screws in the middle. One of them says "ground here to test". The other one might have a round gray plastic cap over it. Pop that cap off to take a voltage measurement there, or, it will be the same voltage as on that yellow wire.

When the generator is not working, ground that test point while the engine is running and you're measuring battery voltage or watching the head lights. The voltage should go up. If it does, all of the wiring is ok and the regulator is not turning on. If the voltage does not go up, measure the voltage on that point and on the yellow wire or screw that had the cap.

Just so I'm clear and don't overlook something, also measure the voltage on the fat black / orange wire while the engine is running.

Caradiodoc
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Monday, November 8th, 2010 AT 2:44 PM

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