Alternator should put out between 13.8 and 14.6 normally depends on the loads you have on.. Yeah 21 is not good, never seen one put out that much.... If it fluctuates from 13.8 to 14.6 I would say alternator. They are nice and cheap also..
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Next update... the voltages I read on the top post of the alternator were with the cable still connected to the post. I disconnected the cable and read the alternator output only, and it was fluctuating between 21.5 and 23.2 vDC! What the... ???
It did that because you disconnected the alternator from the load. The voltage regulator did not see a load so it opened up to max voltage.
When I bought my 96GT, first thing I did was put in 2 new MSD coil packs and wires (almost Two years ago), about 2 months ago the car started hesitating and sputtering; mine is a 5 speed also and in neutral there was no problem, changed plugs, changed fuel filter, cleaned maf & iac valve (3 different mechanics including a ford dealership) nothing changed. Eventually decided to Check everything myself, found one of the plug wires had turned rust green and the coil terminal for the # 8 cilinder was rusted green & acid like; ordered two new accel coil packs and motorcraft wires, installed them myself and the car runs better than when I bought it, anyone has an idea what can cause the acidic rust on the wires and the coil pack?
OK, new update... replaced alternator yesterday... no longer getting the battery light, and voltage at the battery reads a constant 14.26 vDC. However, now the battery (which is only 6 months old) won't hold a charge overnight. I disconnected the negative battery cable, hooked up the Fluke to read resistance between the negative and positive cables, read approx. 686 ohms, and started pulling fuses from the main underhood box. When I pulled the fuse for the power seats, the resistance shot up to around 99K ohms. Put the fuse back in, disconnected the harness under the driver seat and it still read the same, so apparently the problem is in the wiring between the box and the harness, not the seat itself. Pulled the seat fuse again, and then I pulled the generator fuse, and the meter took off to the Mega-ohms range. Isn't 99K ohms a bit low for the alternator? I pulled the lead from the alternator and read it from the post to ground, and got the same 99K ohm reading, so it's not the cable.
It is driving WAY better, but after driving it for about 120 miles last night, I goosed it and it bucked again around 3500 RPM.
Well, after getting 3 failed alternators from O'Reilly's, I got one from the dealer, and lo and behold, it worked! Car is running like a scalded dog. No charging light on the dash, good steady voltage at the battery, no hesitating or stalling when droppin' the hammer. Thanks for your help guys!
