The temp switch (which is often blue) can be tested by either removing the plug, or jumpering the two leads, depending on model. This should start the HIGH SPEED fan.
The receiver-dryer is behind the left headlight. If you jumper the leads the LOW SPEED fan should come on.
It is possible to have one speed and not the other -- that's why it's important to check both. If high speed works but not low speed, check the big resistor near the receiver dryer. A frequent failer.
You can tell warmer weather is here by the # of aux fan posts. . .