4wd won't engage

I have a 1999 Trailblazer. My 4wd won't engage. When I push the button the light to the 4wd flashs like it is going to engage but it doesn't. Someone said it is a solenoid on the treansfer case? Is there a way I can check this?

My colorado was doing that yesterday, I let it roll a little bit and it engaged everytime.

its the vaccuum actuator underneath your battery. mine did the same thing its an easy fix, and its only bout 50 bucks. i suggest you get a haynes manual, it will save you alot of time tryin to figure out how to remove the actuator. you have to pinch the cable somewhere, but i forgot where. if that doesnt work let me know

Could be the small vacuum switch on the fire wall.

http://img.photobucket.com/albums/v448/therealsundance/DSCF0049.jpg

I would check this first before I was my time taking out the battery. Just pull the hose out to the switch and see if there is vacuum to it. Put it back on, take the hose that is going to under the battery off. Engage the 4x4 and see if there is vacuum. If there isn't, that's your problem, if there is, well, take the battery out and check the other actuator.

My daughters 95 blazer had the same problem. I took it to a mechanic friend and he replaced the actuator or a sensor on the top of the trans transfer case. Although i wasn't the to do it, I was there while he replaced it. He was on his back and reaching way up on the top of the trans to do it. It didn't take him long and that fixed the problem. Give it a shot.

There is a $15 3 port vac switch on the drivers outboard side of the transfer case (look up by the front driveshaft on case) that can leak or the vac lines can be cut/rotted out. For 98 and older this switch is on the transfer case but on 99up (newer) that 2 port on the firewall replaced the 3 port. Just did a 98 and the switch had a leak in the plastic housing. There is a formed rubber connnector on top of the switch with a pin so you can't put it on wrong (well a really stupid person could I'd guess). 7/8 box end wrench removes switch.