Why won't the 4 wheel drive won't engage on my 1994 blazer s10?

Answer 1

The s10 4 wheel drive systems are vacuum activated and most problems with engagment can be traced to 3 possible culprits - leaking vacuum lines, faulty transfer case vacuum switch (part # 89059420) or faulty vacuum actuator (part # 25031740) which usually is located under the battery tray. These are all relatively cheap to replace. If you have push button engagement (on the dash) listen for engagement at the transfer case when the button is pushed. If you don't hear it, you may have a problem with your Transfer Case Control Module (TCCM) (a small metal box under the dash) or your Transfer Case Encoder Motor which is mounted on the side of the transfer case. The encoder motors are more expensive but can be purchased on eBay and elsewhere. There are ways to test/troubleshoot both the TCCM and Encoder motors but might not be advisable unless you're pretty mechanically inclined. Good Luck!

I have owned a 1994 S10 4x4 Blazer now for 6 Years, It seems every time I have some stupid problem with it all I have to do is "REBOOT REBOOT REBOOT" JUST LIKE ANY Computer today it seems to work on most this crap you read about on these trucks, when the 4x4 won't engage or when it wont disengage, the very first thing I try is pull the + positive cable off the battery and hold it to a ground to dump all the power from the system (IT RESETS EVERTHING) and to date this method has never fail me, try it you can't hurt anything and it could save yourself a lot of time and money.