i have a 94 s10 blazer 4x4, and im having problems with my 4 wheel drive.
what happens is that i will go into neutral, and press the switch, sometimes it will engage into 4 wheel, sometimes it wont, then when i want to come out, the same thing happens, sometimes it comes out ok, sometimes it wont. what should i be looking for? im a ford guy myself so im not sure about these gm vacuum 4x4 systems. thanks!

 

Could be a connection problem to the TCCM. Could be an intermittent encoder fault.

I would inspect all of the electrical connections from the switch to the TCCM to the encoder motor on the side of the transfer case.

 

I am having a very similar problem, only my 4 hi wont engage at all and the 4 lo will sometimes and then not come out of it. Hopefully we can come to a conclusion together. Some of the guys told me to check the vacuum lines and make sure nothing is loose, and someone else mentioned to check behind the button if its a push button because sometimes the contacts get dirty and mess up the controls. Hopefully for both of us it's something easy and not expensive. I'll let you know if I figure it out.

 

im sorry lite but i cant help with yours but eff10 my 94 was doing the same thing, i went to the junkyard and got a new push button switch and it cleared it right up. I am currently having a problem with mine now also if i may ask it here "i dont want to hijack the thread" but my 4wd switch will only blink both lights no matter if i try to go into 4Hi or 4Lo and sometimes it wont even do anything like it doesn't have power would either of you guys have any ideas?

 

I found the answer to my 4x4 problems with this thread https://blazerforum.com/forum/tech-articles-diy-29/4x4-no-worky-maybe-will-help-7180/
It's easier for you to just read it than for me to explain it to you.