hi all . i have a 2001 chevy blazer it has 4button 4wd.the problem started when i pushed the auto4wd button the light started flashing but never engaged 4wd. after joining this forum and doing some searches i came up with some great info .i removed the battery and saw the switch i saw a vaccum line running to the area around the distributor.there i found the vacuum line was corroded and broken . on the firewall i found a small cylinder that had a peice of the same line that was broken off of it so i attached it and now my 4wd lo light comes on solid and when i try push the 2wd button i get no response at all. i cannot seem to find on the transfer case the t.c.vacuum switch. i done alot of searching but i cannot seem to find where its at .any suggestions you all have would be most greatly appreciated.

 

Since you have the 4-button switch (aka NV236 transfer case), you do not have a mechanical vacuum switch on the transfer case itself, but rather, an electronic solenoid on the firewall.

There are a lot of things that affect the 4wd system on these trucks. Vacuum supply to the front axle engagement actuator is one of them. Corrosion at the switch in the dash, TCCM in the passenger side kick panel, and on the encoder motor on the side of the transfer case is another issue that can sometimes easily be remedied.

 

well i went back out and i connected the vacuum line to the soleniod on the fire wall shifted the truck into nuetral and rolled it into auto4wd. when i turn the key to the on postion all 4 of the lights come on . after the truck is started only the auto 4wd stays on and no other light responds when their button is pushed. thanks for the good suggestions . .