I finally found out what the problem was. One of the wires had corroded at the connection to the fan clutch, so no power went to the temp switch. It took me awhile to trace the wire from the temp switch as it went into the wiring harness for the glow plugs six inches then turned around and went back out to the fan clutch. I resolderd the wire back into the connector, now the fan engages as it should when you jump the temp switch.

Chris