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Old 10-30-2016, 08:02 PM   #12
ray_mcavoy
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Join Date: Nov 2009
Location: Sherman, ME
Posts: 2,373
Re: Internally regulated 3-wire alternator conversion

Quote:
Originally Posted by Scooby63 View Post
I have everything pretty much sorted out, with one question.

The BROWN wire that comes from the cab harness is 12V when key is on.
The WHITE wire that comes off the pigtail in the #1 tab on the alternator is 14V when running.

Are these 2 supposed to be spliced to each other ??????

Reading a few write ups it sounds like I am supposed to connect these 2, but it seems wrong to connect one wire with 12V to another with 14V
Yes, if you are using a 10SI or 12SI alternator, the brown wire that comes from the cab harness should be connected to the alternator's #1 terminal.

The reason you're seeing the 12V vs. 14V difference is because you are measuring under different conditions (one with the key on and the other with the engine running). Also, the brown wire is connected to battery voltage through the "GEN" light on the dash and a resistor wire (or just the resistor wire if your truck has factory gauges). So in cases of a malfunctioning alternator the voltage difference across the bulb will be large enough to cause it to light, indicating a problem.
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