I bought a 00 blazer about 8 months ago. They said the only problem was that it was stuck in 4wd. Simple fix, I just unplugged the negative battery terminal and reset the computer. After this I realized the ABS light was on. turns out I need a new front hub. I replaced it and everything worked great. Then one morning it was trying to switch into 4wd by itself while I was driving. I replaced the switch in the dash and it fixed it. I cant switch it into 4WD now. I started the blazer and the while it was running i unhooked the battery to I could get a good look at the actuator. I got back in the car and tried switching it into 4WD. Now that the battery was off I could hear kind of a hiss I am pretty sure that it was the actuator. Anyone have any ideas what it could be??? I have already read the forums about this and none of them sounded like my problem exactly. Help please!!!!

 

The vacuum leaving the lines???? maybe?

 

I shouldnt have used the word hiss. It sounded more like a suction sound. Like the actuator was working but something else is wrong.

 

3-button or 4-button?

 

its the 4 button. The only button i can push that will actually light up and flash like it is trying to change the the auto 4WD button

 

You have the NV236 transfer case. I would check the connections at the switch, TCCM, and encoder motor for corrosion. While you have the switch out, you can test the resistance values for each button push (search for "nv236+resistance" with an author of "swartlkk" - both without the quotes).