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Old 10-25-2009, 12:30 AM
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Voltage fluctuation

I have a 2000 dual alternator 7.3 that is having voltage fluctuation issues. Bounces around from the normal ~14 volts to over 18 volts. I tried to isolate it by unplugging the plug on each alternator and the problem is there with both of them. It is totally random and not RPM dependent. I thought it might be the regulators, but these alternators were rebuilt within the last couple years and I find it suspect that both would go out at the same time. The batteries are new as well. Everything starts and operates as it should except the fact that the voltage spikes up (which can also be seen in the lights).

I'm wondering if it could be an issue with the sense wire signaling.

Any ideas??

Thanks!
Greg
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Old 10-27-2009, 03:26 PM
Johnny Law Brown

 

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It could be the regulators I would check them just to be sure.
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Old 11-23-2009, 07:00 AM
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I'm having a simular problem with my 2000 ex. (1 alt) can u tell me how or where can I go for more info on checking the regulators. Thankx
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Old 11-23-2009, 07:11 AM
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It wound up being the regulators. I had rebuilt the alternators a couple years ago and used aftermarket regulators. I replaced them this time with OEM Motorcraft ones from High Output Alternator, 200-250-300-350 Amp Alternators, high output alternators, Delco Remy,Ford Truck Alternators

The way I tested was unplugging the alternators so that only one was functional to see if it was one or the other. Since they both fluctuated, I knew is was a truck wiring problem OR BOTH alternators had an issue.

The only reason the alternator would put out more voltage if the alternator was in good condition is if the sense wire was picking up a low voltage and the alternator was trying to compensate. To eliminate the truck wiring as the culprit, I wired a jumper from the sense wire to the battery positive. This way I know the alternator is seeing battery voltage and not a drop from where ever it normally picks up the signal.

It still had the high voltage jumps, so I determined it must be the alternators. Ordered up the regulators, swapped em out, and all has been good since.
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Old 11-23-2009, 04:50 PM
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Hey thanks alot I'll look into it. I appreciate the assistance
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