97 3.2L Alternator/Electrical issues

05-31-2005, 10:49 PM
Let me first say that I have searched extensively through the threads and thoroughly read everything I could find. On to the issue...it's a 97 3.2L Passport. Over the course of the last month or so, the voltmeter has taken to dipping noticably at times while driving. Say, for the 14.5 to the 13-13.5 range. Nothing too crazy, and I do realize that some fluctuation is normal. Now, as of three days ago, it just started dropping right to the 12V mark. When this happens, the battery indicator comes on as would be expected, and the AC cuts off (though it's rarely on anyway).

Upon further investigation, it seems that 2200 RPM is the cutoff point for the truck acting normally. As soon as it hits 2200(ish)RPM in any gear, thats when the voltmeter drops. Let off the gas and let it slow, and it will go back to 14V. This happens at about 1500-1600 RPM, and it's real obvious too in that at pretty much the same instant, the tach will drop about 600RPM like it's suddenly affected by the alt's parasitic drag again. I've tightened/loosened/check the belt to see if maybe it had just developed a new favorite tension or something, but no. Had the battery and alt tested with the portable tester at Advance Auto, and later went home and removed the alternator and had it put on the bench tester. Everything tested good, but of course most of their testing is done at idle and 2000RPM. Checked everything at home with the meter, and seems fine. I'm just trying to figure out if it makes sense that the alternator would be crapping under load like this, if it's the internal regulator, or if there's something else I may be missing. If anyone has any thoughts I'd sure appreciate your ideas.

05-31-2005, 11:41 PM
I developed the same problem when I replaced my dead stock alternator with a bosch reman unit. I'm going to take it back and exchange it for aother one this weekend and hope that solves the problem I'll post the results.

06-01-2005, 08:52 PM
cool...I'd really appreciate hearing whatever you find out on that.

06-05-2005, 05:47 PM
Update...was the alternator/voltage reg for sure. Just replaced it this morning, and it runs great!

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