2.0L air cooled devon.
I ended up driving 15 miles with the alternator removed (see other post

When I arrived, there was smoke almost billowing out of the air intake vents. Fired my water mist air extinguisher through the rear flap just in case, but no fire apparent.
I assumed that the only need for the fan on the alternator was to run the heating system - which doesn't work anyway, as I've disconnected the pipework forward of the heat exchangers.
So I'm trying to understand what caused this, and my guesses were:
1. Fan on alternator IS required to assist engine cooling.
2. Oil burning off heat exchangers coming back into the engine compartment due to now having no alternator related air pipes connected.
3. Low battery causing weak spark causing engine to overheat.
Are any of the above possibilities do you think, or is there some other possibility I haven't thought of ?
Is it OK to run it a short distance with the failed alternator removed (battery allowing).