The International Cessna^® 170 Association

There are other differences also, depending upon the particular installation. Automotive alternators that are belt-driven operate in opposite rotation than aircraft alternators. This requires a change in the cooling fan.
Automotive alternators are not "marinized", like marine and aviation alternators ... (to improve corrosion resistance and to reduce arcing at high altitude, aviation alternator rotors and stators are treated with insulating coatings that automotive alternators usually lack.) It's doubtful that low-altitude (below 10K) would have adverse affects on automotive alternators, however.

In addition to what George stated. All of the Ford automotive alternators I have taken apart have wires going to the pin (threaded lug) for the stator. The airmotive alternators I have rebuilt do not have this wiring. In the Airmotive Alternator the stator pin (lug) is just there to help hold that portion of the Diode plate to the inside of the housing. They are not the same animal no matter how many people have told me so. I have rebuilt both of them many times. There are component parts such as the housings, brushes, brush holders, and other things that are interchangeable. I used to always keep brushes and bearings in stock to make repairs. Parts were purchased at reasonable cost from aircraft parts whole salers. We always removed the alternators from our fleet of Cessna’s and inspected the alternators at 500 hour intervals. However in the later days if I found anything wrong with them I quit repairing them because Aero Electric (Kelly Aerospace) started potting all of the components in so that they could not easily be repaired and returned to the same condition they were previously in. I have other issues with these particular alternators as rebuilt by Kelly Aerospace but will not go into it here. Alternators rebuilt from other sources and airmotive accessory overhaul shops have been my preferred source.

Regards,

Jim