iv got a 99 4x4 it wont stay engaged in 4x4 has new diaphram that was under battery tray and has a new tcv switch that was on top of transfer case im pretty sure my hoses are good also my heater control selector does nothing heat comes out at defrost and vent at same time any help would be greatly appreceiated also the tccm under the kick pannel clicks when buttons are pushed it goes in 4x4 for about ten feet from stop then slips out

 

You have a vacuum leak that you need to find. The front axle engagement actuator & the HVAC system both use manifold vacuum to operate.

 

iv got good vaccum at the diaphram seems to be pulling cable far enough could there not be enough vaccum when connected the diaphram sucks all the way in

i just got this blazer and i believe the dash has been removed also there was alot of screws missing

 

How far is the cable being pulled?

3-button or 4-button switch in the dash?

 

its being pulled atleast a half inch or more i cant make it sqeeze any further buy hand it is 3 button 4x4 2hi,4hi,4lo

 

0.5" to 0.75" is the proper range of motion for the actuator.

The next step is to jack one front wheel off the ground. With transfer case in 2HI and the actuator/cable pulled in (either manually, or by applying engine vacuum directly to the actuator), try to spin that front tire. If the front driveshaft spins, then the front axle is properly locking in place. If it doesn't, then you have a problem with the front axle engagement mechanism.

 

ok i do believe tyhe cable is beeing pulled far enough as i can feel it engage but as soon as i put any load on 4x4 it clunks and slips out it does it in 4lo and 4hi i have air blowing out my dashvents and defrost vents it doesnt change when i move switch either could the 4x4 problem be my shift fork or maybe i dont have enough vac what does vac bleedoff do does the 4x4 bleedoff to stay engaged

 

My 2000 Blazer is doing the friggin exact same thing! I think it's a vacuum leak but i'm not sure where

 

im going out in a minute to change heater control just fir the heck of it lol could it be that i dont have the resivoir for the vaccum on driver side of hood help im lost lol

changed heater control and nothing happend got to looking under behind glovebox heard a slight hiss so i think hearing is bad lol on the heater vac hoses there a grey one that goes to a actuater od somesort i unpluged the hose from the pump and plugged it and now my heater vents work great still no 4x4 boo hoo

 

Where exactly is the hose you unplugged in the dash and how do you get to it? Picture?