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Simple alternator upgrade -- 55A to 94A


rich weyand:

OK, so I got carried away.  First there was the powered subwoofer.  300W, or 25 amps peak draw.  Then there were the Hella 7" round replacement glass with Philips Xtreme Power bulbs.  11 amps.  Then the replacement bumper with the integral fog lamps.  9 amps.  Finally the Flexalite Syclone electric fan.  18 amps run and maybe 30 amps on start-up.

I have been waiting for the 10SI 55 amp alternator to die, and it did.  Lost a diode, I think.  Anyway, it won't lock in at idle any more if even just the headlights are on.  So, time for a replacement, which means time for an upgrade.    ;)

Yes, you can grind brackets and change wiring and change pulleys or go serpentine, and then run the 105 amp CS130.  Or you can just buy a 12SI 94 amp alternator, and swap it out with no other changes.

The one I got is from O'Reilly's.  It's their part number ULT 01-0266.  They stock these all over as they were ubiquitous.  $70 plus a $15 core until you bring the old one in.  It lists as for a 1984 Chevy Camaro with the 305 G-code engine as one example.

One change I did make.  I did not hook up the stock charge wire to the BAT connection on the back of the alternator.  That 12 AWG wire down to the starter is not stout enough for 94 amps.  I cut the connector off the end and put some shrink wrap over the end to keep it out of trouble.  Then I ran a 6 AWG wire from the BAT post on the alternator directly to the battery POS terminal.  I loomed it with the negative battery cable so it's not obtrusive.

Works great.  No more problems keeping voltage lock, even when I am running lots of lights and loud stereo and the cooling fan kicks on.   8)

Here's a good resource on the 10SI and 12SI alternators.


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