OK I couldn't resist so I pulled the car back in. When I put the hot 12V on one side I got the high speed fan. When I tries the other side I got nothing. When I check for continuity the resistor isn't "open", so what's going on. I took the wires off the resistor and the problem is now clear. The side with the 2 wires wasn't properly installed at some time in the past. It was a little loose, and the contact area on the resistor is totally rusted. It's impossible to clean it up so I'll drop by the dealer tomorrow and get a new one. The problem should be solved. Thanks for your help.

Pete