I "fixed" it using the mess around with it until somehow--who knows why really--it works.
The resistor was OK--read 8 ohms. I did clean the smoke unit some more. Perhaps I had put in too much smoke fluid and that had caused an excess load on the fan motor. Also, I noticed a few wires routed under the fan motor that seemed to be pressing against the leads to the fan motor. I couldn't really see--the wires are fine and my eyes are not--if the normal heat in the fan motor leads might possibly have melted just enough insulation to short a motor lead against one of the three other wires. Just to be safe, I moved the wires apart.
Anyhow, not sure why, but we're smoking again. Thank you, Zachariah, Sean, and John, for pointing me in some useful directions.
