4x4 problems 93 S10 Blazer 4dr

93 S10 Blazer 4x4 4dr.
In year 2000 I had to replace the ? cant remember the name of the thing that engages the front axle.
Well yesterday I needed 4x4 in a bad way and pushed the button, you could here the click sound under the dash and the green light go on steady, but the front end did not engage. Almost made me pay for it on a icy overpass.

So what do you think it could be and how do I troubleshoot this?

When the very expensive part went out in 2000, the push button would just flash when pushed. This time it reacts like normal and turns green and stays steady lite, except the front end is not engaging.
Give me ideas where to start folks. Thanks.

I think the part that was replaced in 2000 was called a encoder? Not sure, it was $400-$500 new at GM. It engages the front after pushing button.

Anyhow was trouble shooting being nobody posted any ideas here.
The vacuum lines seem OK and I didn't find any crack etc, (that dont mean I missed it on top of the trans and case).
Pulled fuses and checked, unplugged battery for over 30mins still nothing.

The light comes on and stays steady green for 2H. The switch under the dash I can here clicking like normal.
I swear at 55mph-65mph when I push the button for 4x4 I can here and feel (little clunking) the front end engaging. But at 35mph and stopped nothing.
When checking by turning in 2H and 4L on dry pavement to see if it has the front engaged nothing.

So where is these vacuum switches or etc to start checking to see if they are bad?

http://www.automotiveforums.com/vbulletin/showthread.php?t=572914

Does the front drive shaft engage or lock in?

Will it shift in if you stop and then back up and roll forward?

The front drive part does not lock in.

Stop, go back and then roll forward nothing happens. Still just a green
steady light always.

I read your link for the 98 and up, what can I take from that for my 93 older body style?

I have a steady green light, not a flashing light like in the link.

Where is the actuator on a 93? under batt too?
Where is the transfer case switch on the 93?

How do i check these to see if they are working?

Does front drive shaft lock in in 4W drive>

When you try to shift to 4W what does the 4W green light do.
Like blink and the come on or just blink or not come on?
If it blinks and comes on then check front drive shaft for locking in.
Report back if locking in or not.

Front does not lock in.

Push 4wd button it turns green and stay on just like it did when all was OK and worked. I would call it one blink on and steady green.

I am going to try and jack the blazer up where all 4 tires are off the ground and see if the transfer case is turning the front shaft when 4x4 button is pushed.
If it is turning what do I look at actuator?

If it doesn't turn do I look at that vacuum switch in the transfer case with the ball bearing?

Somebody here has to know something about the older gen blazers 93 and trouble shooting.

All fixed, 4x4 working.

Less then 2 hours and $54 dollars total with tax for part.

Got a break in the weather today and got up in the 40's (figure this was my shot to crawl under and work, so I jacked up the blazer on all fours. Started and put into gear. Then clicked 4x4 button, front shaft turns but no front axle.
Checked and removed switch in front axle, seemed fine.
Removed battery and battery tray. Actuator had a tear in the rubber skin. Replaced and all is fine.

Thanks for posting back how it went and the fix.

If it wasn't for peoples past fixes posted and people leading me in the right direction of where to look for the problem. It would have been alot tougher to figure out on my own. Thanks for the tips.
2 for 2 on fixes here now from a CPI unit to 4x4 fix. Just wish I had knew about this place when the encoder went out back in 98-99, could have saved myself a bunch of money on the fix and part.

Keep up the good work helping us out guys, Thanks again.