To work on a T100 model, start by pulling the battery's cable off the negative side and make sure the anti-theft audio system's lockout is turned off if your car has it. To start, turn off the airbag, detach the steering wheel, then remove all shielding from the steering column. Disconnect the electrical wiring where you control the windshield wipers. Using an ohmmeter, check the continuity of the switch terminals: For the mist-type wiper switch, your ohm-meter should read continuity between terminals 4 and 8 when you're on MIST, terminals 7 and 8 show continuity when on OFF, terminals 4 and 8 again show continuity on LO, while terminals 4 and 9 show continuity when on HI. In the OFF and INT position, you should find continuity between terminals 7 and 8 for the intermittent-type wiper switch. For INT, LO, and HI settings, check for continuity between terminals 4 and 8 for terminal 4 and 9 for terminal 4. To test either washer switch, keep pressing the on/off button. You should not see any connection when the switch is off, but it should connect terminals 1 and 2 when you turn it on. When the switch stops working, you need to get a new one.