i have a 2000 chevy s10 blazer and the 4 wheel drive wont kick in. 2hi works fine but when i click it into auto 4 wheel, 4hi, or 4 lw the light just blinks and it doesnt kick in. i replaced the switch and i took the module off and had no corrosion there, im not sure what it could be...

 

Does it stay flashing or does it boot you out of 4w and back into 2, and do you get a service 4wd light?

 

sorry for the delayed response, its been one of "those" weeks.
the lights on the button i push just keeps on flashing but DOES NOT go back to 2wd. and the odd thing is that with this whole problem, i have yet to see the "service 4wd" light come on...any ideas on what it could be??

 

I would check the vaccum lines all the way to the front diff actuator and the actuator itself. Also check to see if the solenoid on the firewall is working, vaccum should be coming out the top of it in 2w and should stop when switched to 4w.

 

fyi... the most common thing for these vacumm operated systems is for the hose to fall off the actuator under the battery box.. i don't know why gm had to mount the thing with the hose pointing down. also check to see if the actuator holds vacumm by compressing it by hand and holding your finger over the vacumm port. it should suck the rubber in. if it does'nt than replace the actuator. you can also see that the cable to the front diff. is connected and hear the diff click or engage. hope this helps. good luck and keep the shiny side up!!

 

your light blinks because your diff wont engage. take the battery and tray out, then put your truck on jackstands all around(and make sure all 4 wheels are OFF the ground), find some way to wire the battery without it getting in the way. start the truck put it in 4wd and hand squeeze the actuator. once you feel it click in the light will stop blinking and youll have 4x4.
mine had the same problem, so i just ran a pull cable into the cab. so now whenever i need 4x4, i just push the button (and watch it blink) then lock the front diff with the pull cable(and watch the light stop blinking). once it stops blinking, i know the front diff is engaged and ready to go. cost me like 30 bucks at napa for the pull cable, but this way you wont have to worry about any vacuum lines anymore cuz now its manual.

ps. if you dont feel the actuator squeeze to good, then rotate the wheel a little bit, and you should feel it lock in place and squeeze more.