bigrichard,

I'm a little confused. You say you don't operate it in traffic because you don't know if the fan comes on. You won't KNOW if the fan is coming on UNTIL you are in traffic conditions. It only comes on in the event of excessive high side pressure in order to prevent damage to the a/c system.

In a mild climate (since you choose not to list your location I have no idea what your climate is) it would be possible for a properly working aux fan system to live its life without ever coming on.

Go to the high pressure switch at the r/d, disconnect and short the pins on the connector to see if it comes on. If not the problem is with the wiring between there and the fan. If it does, and the fan still does not come on at the specified high side pressure, then the high pressure switch is bad.

BTW, I don't remember which one, but I think that it is the high pressure switch that is actually a temperature switch. In the a/c system pressure is indicated by temperature, so they use a temp switch to sense excessive high side pressure.

Good luck,