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Old 02-08-2013, 10:40 AM   #1
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Exclamation Alternator problem, please help

Why would an alternator only work when the voltage regulator is unplugged


When the car is running and the voltage regulator is plugged in with the three wire connector on the back of the alternator it does not put out any voltage and the battery voltage drops to 11.92v. There is no indicator light on in the dash, but both my DVOM and a Snap-on battery/alternator tester confirmed the alternator was not working with the voltage regulator plugged in. I checked continuity from the alternator all the way back to the pcm on the gray and blue wires and they both had a good connection and the red wire had good continuity and voltage.
If I unplug the voltage regulator the Snap-on tester showed the alternator as good, but the indicator light on the dash lights up.

All I can think of is maybe the PCM needs reflashed or replaced??? It does have a custom tune by FSWerks for the supercharger. Is this a likely culprit???

I'm at a total loss, please help!!!


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Old 02-08-2013, 11:11 AM   #2
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How is you've eliminated the alternator?! The voltage regulator is integral to the assembly, if that goes bad you get a whole new kit 'n' caboodle.
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Old 02-08-2013, 11:26 AM   #3
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I've replaced the alternator twice (less than 10 miles on the last one, thought I just got a dud). I had the alternator tested and it worked as long as the voltage regulator is not plugged in. I don't know why this would happen? Although I did find where I can get replacement voltage regulators for it.
http://rebuilderinabox.com/6g-8260/
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Old 02-08-2013, 12:35 PM   #4
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Called FSWerks, they assured me that it is not possible for the tune to fail and cause this. They explained that it would not work at all if it failed. They suggested faulty wiring, but I've already tested everything that I know how. If you guys have any tips on ways to test it, please let me know.
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Old 02-08-2013, 03:05 PM   #5
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Electrical gremlins are terrible, you may have to check each individual wire from battery to alternator . And do a process of elimination. If this has just started since you put the supercharger on. Start checking wires around any of the connections with it. And check close to anything that maybe around the hot exhaust.
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Old 02-08-2013, 03:20 PM   #6
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It's had the S/C for years and it has no electrical connections, this problem just came up recently. I'm beginning to think corrosion in the wiring harness I'm going to try load testing all the wires from the alternator harness to the PCM and fuze box tomorrow. Just to see if maybe they have continuity but are too weak to handle a load. I really don't have any idea what else to do. I think when I move back to the US in May, I'm going to buy an old 60's-70's pickup so I don't have to deal with this stuff anymore.
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Old 02-08-2013, 04:01 PM   #7
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When I changed my alternator out I went ahead and upgraded my ground wires and also upgraded my wire from the alt to battery. As a safety measure and for piece of mind since I have a lot stereo equipment.
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Old 02-08-2013, 04:06 PM   #8
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Quote:
Originally Posted by Capt. Obvious! View Post
Why would an alternator only work when the voltage regulator is unplugged


When the car is running and the voltage regulator is plugged in with the three wire connector on the back of the alternator it does not put out any voltage and the battery voltage drops to 11.92v. There is no indicator light on in the dash, but both my DVOM and a Snap-on battery/alternator tester confirmed the alternator was not working with the voltage regulator plugged in. I checked continuity from the alternator all the way back to the pcm on the gray and blue wires and they both had a good connection and the red wire had good continuity and voltage.
If I unplug the voltage regulator the Snap-on tester showed the alternator as good, but the indicator light on the dash lights up.

All I can think of is maybe the PCM needs reflashed or replaced??? It does have a custom tune by FSWerks for the supercharger. Is this a likely culprit???

I'm at a total loss, please help!!!
Could your voltage regulator need replacement, too? I've had alternators and voltage regulators go out simultaneously, and it was a "Which failed first?" type of question.

EDIT - Nevermind. Looks like it's integrated into the alternator on the Focus.
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Old 02-09-2013, 09:29 AM   #9
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Question ECU W/ custom tune replacement questions

Why I think I need to replace it
After much diagnosis and trouble shooting, I've come to believe that my ECU is shot. It appears I no longer am getting signal to my voltage regulator telling my alternator to charge. I've checked continuity and voltage drop on every wire related to the charging system. I've replaced the alternator twice and the battery once. Checked every ground under the hood and cleaned and tightened every connection on them. I've done every bit of diagnosis I can do that I know of without an oscilloscope or access to the Ford PID's. Nothing has changed the results. The only thing that has worked to allow the alternator to charge the battery is to disconnect the wire harness from the voltage regulator. This allows the voltage to go to 13.8v (with the engine running) opposed to 11.9v with the regulator plugged in.

What I think I want to try
I want to try replacing the ECU if I can find one to see if that fixes it, But I need to know what I will need to do to flash the ECU. I have the SCT flasher unit with the current good tune on it (yes I even tried reflashing it). Will I be able to use this to flash the new ECU or will I have to buy an additional program or something to make it work? I'm afraid it may not mate to the new ECU since it's already been use on the one that's in the car. I'm not sure if the SCT units work like that or not.

The ECU connector has "LUY4" written on it. Is this the number of the ECU I would need to buy?

Other options
My last resort is to rig up an older style system somehow. Either using this alternator with the regulator disconnected and using an external regulator, or even an older style alternator with external regulator. this will however turn on the indicator light on the dash, which I would like to avoid.
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Old 02-09-2013, 10:02 AM   #10
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You need to find a pin-out chart for the signal wire from the PCM. You should also try to find the values for the correct voltage you should see under normal operations to further confirm it's the PCM before you spend all that money!
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