The factory 66 and 78 amp stators are absolutely one and the same. The 78 ampere rotor has a much fuller rotor bobbin fill, but different size wire. Both yield a 2.8 ohm resistance at 20c
The 7278 (Lester Number) rotor, the one with the filled bobbin, is the same as the 7294 rotor.
The PROBLEM is the 94-amp stator. Delco took a handfull of stupid pills. The 94 amp stator has far less copper wire in it than the 66 - 78 amp stators.
SHORTER lengths of wire have less resistance. The 3-2 WYE winding HAS TO HAVE higher output because the wires to the WYE connection are SHORTER.
Less surface radiation area coupled to 8 amps higher current equals disaster.
For around 20years I REFUSED to sell a 66-ampere 12 SI to a motorhome owner, nor did I sell a 94 amp alternator to -anyone-. Neither was on my shelf. I DID sell 78-amp 12SI's to motorhome owners, and I DID sell 115-amp DELTA stator 7294 alternators. I would not even FIX a 12-SI unless the Frisbee fan got exchanged for a 13-blade Delco 10DN fan. Auto Diesel Electric in Reno Nevada went the extra mile and ordered a (crate of 350) 10DN fans for me. I never EVER had a 10 or 12 SI warranty using the 13-blade fan.
You will need to exchange FAN SPACERS between the 6203 bearing hub to fan, spin the turbine fan out the back window, take off the spacer between the fan and the pulley, then use a regular pulley off most any alternator with a 17 mm rotor shaft. The wave washer (not a split washer) is the best locking device.
You can find a 13-blade fan in any junkyard. They came standard on early Delco 10DN alternators. Every one of the 13 fan blades are equal. Sharp tips. Ford alternator fans look sort of similar but the outer circle has fan blades with flat tips. They work HALF as well as a genuine 13-blade fan.
It is KRAP like this that reinforced and reassured me that as a young engineer, my employment span in a corporate atmosphere would be measured in minutes. Delco with this turbine fan nonsense, Ford with their insane IAR second generation PLUG IN fast-on terminal battery plug. Push-on .250" terminals for 75 amps! These boys needed a pneumatic rhino dart in the butt and permanent internment in a THICK lined rubber room.
I was supposed to hire on as an engineer? Hahahahahahahahahahahaha in your freakin' dreams!
