93 S10 Blazer 4x4 problem (4WD problem)

My last post didn't have a descriptive enough subject title so I am reposting with a better subject. I am having a problem with getting my 1993 S10 Blazer's 4x4 switch to work. Basically the problem is that it won't activate. The lights come on on the switch when the key is turned to the on position but, it won't turn on when I actually hit the switch (hi or low). What are some common problems with this system? And where are things located that may need to be worked on or replaced? Thank you.

Switch bad, bad vaccum under the battery for the 4x4 diafram, switch on top of the t-case shot.

Agree with troy, I have a 93 also and my problem was a broken vacuum line on the diaphragm that engages the front axle. it is under the battery tray, so you may have to take it out to get to it

Pretty soon I will be removing the totally rusted out fenders on the blazer so, when I do that I will check that diaphragm. Thanks.