i have a weird problem with mt four wheel drive, i push the button, i hear the click in the right side, so i know the module works and i hear the tranfer case shift(both into hi and lo) but it doesnt engage, some one told me it could be a vacuum switch, but before i change parts i figured i ask you guys...any ideas? thanks in advance

 

Sounds like the vacuum switch is getting stuck. Just remove it and clean it out. The switch is located on your transfer case and you'll see 3 hoses going to it.


Btw thanks to Kyle for the above picture. I'm currently using this to clean out my vacuum switch.


And if you are still having problems, then remove your battery tray and check the Vacuum Actuator, they are known to go bad as well.

 

My 2004 Blazer was not going into 4 Hi, i traced the vacuum lines and jiggled some wires and now it works. I found the vaccuum line in your diagram, line B, which you have vented to atmosphere. This line is sucking in air, like a working vaccuum in all modes, 2wd, 4 low and 4 hi. That does not seem right and I was wondering if it was normal.