[Second Series]

I just went through some trouble with my T-case switch. My truck is 1990. I found that the switch is normally closed at rest, so most of the time when the truck is in 2wd, the switch is being activated(pressed) so that it is open. The rare occasion I shift to 4wd, and the switch gets to relax, closing the contacts. I replaced the switch twice. If you check the switch with an ohm meter, it should read closed, or zero ohms with nothing pressing the ball. Now with the ohm meter connected, press the ball it should read open at some point and stay open as you press the ball all the way. The first switch I purchased read closed, open, closed before I installed it, after it failed it was just open. The second one, I brought the ohm meter to the store and tested before buying. I tried to find information about what surface inside the Tcase that makes contact with the switch, but I couldn’t see from several exploded images, so I don’t know if that could affect operation. As a last ditch solution, you could wire a toggle switch to replace the Tcase switch. Attached schematic is for 88 to 9?.