You can test the switch by removing the connector and shorting it. That's how I tested my fans before reinstalling them. The switch actually has two circuits - one for the fans, and I can't recall what the other is for. I do recall that you short either diagonal pair on the connector and one or the other should activate the fans at high speed, and for that reason the connector "clocking" is not important and can be installed in any of the four possible orientations.

The switch itself will not close until coolant temperature reaches 105C, but by shorting a diagonal pair on the connector you can test fan function. It the fans work, then let the engine heat up to 105, and if the fans don't engage the switch is probably bad.

There was no problem with my switch since one fan worked, but the above test will verify that the fans themselves work, which is why I did the test before I installed the frame with the two fans back in the car. After I finished the installation I blocked the radiator with carboard and let it idle until it hit about 105C and both fans engaged at high speed, so I knew the swtich was okay and I did the installation properly, other than polarity on the rebuilt junkyard fan that I found and corrected during the preinstallation fan test.

Duke