the 4wd on my 97 chevy blazer isn't working, so far i've tested the wires and they are getting power, so i figure it's gotta be something with the vacuum system, or something with the transfer case or axle. I took off the vacuum hose on the front diaphragm under the battery and the vacuum seemed to be very weak, however it did move a little when I started it, but it didn't move when i hit the 4 hi button. Any ideas as to what may be happening?

 

https://blazerforum.com/forum/tech-a...ill-help-7180/

 

thank you! exactly what i was looking for

 

Well i did a few more tests, i found that the transfer case is working correctly because I wasn't able to spin the front driveshaft with the 4wd engaged. I then tried to engage the 4wd by pulling the cable attached to the actuator but it would only move about a quarter of an inch. I also tested that the actuator would hold air and it did, but while I had the hose off of the actuator I checked to see how strong of a vacuum it was making and it was barely anything, it even took me a couple seconds to realize that there was a vacuum. Any ideas as to what might be wrong? The different vent settings for the air conditioning (feet, head, defrost) also aren't working, its stuck on defrost, but when i turn it to max a/c it comes out of all of the vents if that helps any. Thanks in advance for the help

 

Sounds like you have a vacuum problem which is discussed in the thread linked to above. I'd start at the engine. The vacuum line hooks up to the same fitting that the PCV hose connects to on the driver side of the intake manifold. From there it should run through a check valve 't' fitting and to another 't'. The three outlets now should run to the vacuum ball, the firewall (HVAC), and the switch on the transfer case.

But you should be able to manually pull the cable at least 1/2" (should be somewhere between 1/2" & 3/4" of movement) provided the splines inside the axle are relatively close to meshing. You could jack up the passenger side to get the front passenger tire off the ground, pull the cable while slowly rotating the tire to see if it will click in. If it won't, then you either have a cable problem or a problem inside the front diff in addition to your vacuum supply problem.

 

Well I was able to figure it out, turns out the line to the vacuum tank on the hood got disconnected and thats why the vacuum at the actuator was so weak and why the a/c wasnt working, and as for the cable i figure it was froze up a bit since it hadn't been used in a while. Thanks for the help!

 

You can try lubricating it. You should get it freed up so it moves rather freely with the only resistance being from the return spring inside the front axle housing.