I have a 2000 Blazer and the 4x4 will not work. The lights all come on, and the transfer case will lock the front drive shaft.

So I removed the battery and the cable going to the vacuum actuator and watched it while engaging and disengaging the 4x4. There was no movement at all. In fact I could not even move the cable with a pair of pliers.

So my question is should the cable going to the vacuum actuator be able to move freely? Is it possible that the cable might just be frozen and the actuator might still be good?

 

if you see the actuator retract its self then its good

if it dont you got a vac leak or a bad actuator

if the cable is hard to pull its possible its seized

 

No movement of the cable is a definite problem. It should move, albeit with some resistance as there is a return spring inside the front axle.

If you couldn't follow Gi0's post due to the lack of spelling, punctuation, and grammar; here's an expansion of the points he was attempting to relay:

If the actuator doesn't retract or at least suck in on the rubber portion when 4HI or 4LO is selected, then you have a problem with either the actuator itself or the vacuum supply to the actuator to go along with your frozen cable.

If it does pull in as it should, then the vacuum side of the system is likely working properly. Any other problems will show themselves after you get the cable working as it should.

Either way, the cable needs to either be lubricated until it moves freely or replaced. I have found the easiest way to get a frozen cable freed up is to remove it completely from the vehicle and apply WD40 to both ends.

 

I also have a 2000 Blazer LT 4,3 v6 (W). The problem I have is that when I turn the ignition on all the lights on the 4wd switches come on for a split second then the service 4wd light comes on. So obviously the whole 4wd system stopped working. What could I systematically check to get it working again? The nature of my business means I need to go offroad all the time and a 2,5 ton rear wheel drive kind of stinks in muddy conditions

 

I replied to your other thread. You have larger problems that need sorting before worrying about the 4wd. Also, please try not to respond to active threads where the original author has not posted a resolution unless your problem is identical to theirs.

 

I have the same problem with the cable being seized/won't engage via vacuum or by manually pulling it. I hope it's just some rust that can be broken up/lubed. Will work on it and post my results tomorrow.