I have a 2000 Chevy Blazer that won't change vent modes to defrost or any other position. I checked the vacuum hoses in the engine bay and decided to replace them. I ran new hoses to the engine, vacuum canister, etc. The problem is still happening unfortunately. I tried blocking the rough looking 4x4 hose that I couldn't replace in case that was leaking enough to not give enough pressure but it's still not working. I guess the next step is too look at the actuator inside the cabin. Where is this located?



Thanks for any suggestions

 

Are you positive you hooked the 3 way vacuum splitter back up correctly that's at the driver's side engine bay by the firewall? It has a built in check valve, and if it's hooked up backwards it will not work at all.

 

Yes, I'm getting a vacuum beyond the check valve. I've unhooked the hose going to the transfer switch and feel vacuum at the splitter. One thing that I learned while researching this problem is that in the event of failure the vent mode should default to defrost; mine is stuck on vent so it makes me think something is jammed up. I took off the lower plastic panel on the driver side and didn't find the actuator. I'm not sure if I'm looking in the right place or how many more panels need to be removed. I did find information on the blend door actuator on the passenger side but not much on the vent door? vacuum actuator.

Thanks for the suggestion

the ???? hose I think goes to the transfer case switch. I need to replace this hose but I need to trace it somehow. I took that hose out of the equation and capped the connector and the issue still occurred.

 

None of the stuff on the driver side will move. On the passenger side the door to the blower motor will open but the horizontal actuator doesn't move. I'm not sure what each of these actuators control and I don't know how to remove them.

 

Starting on the passenger's side, the actuator to the left. The actuator is held in place by a clip; difficult to see as everything is the same color, but it just lifts up and then you can unhook it to see if the internal door moves. This door is for temperature.

However it may be best to pull the dash trim panel off to access the HVAC control panel to see if there is a vacuum leak or worse...trans fluid in the vacuum control. You did not mention if you have manual or auto HVAC; does make a difference.

Also you could carefully remove the vacuum connector from each actuator and then move the actuator arm to see if anything is stuck. Known problem is the defroster door which is internal breaks and gets stuck. Do a search here and you will find info on that. These are the actuators at the center, just to the right of the driver's feet well.

 

This is a manual HVAC system. I pulled the vacuum lines on all of the actuators and I believe only one or two had suction. One was the actuator for the blower door (which works). I don't recall which was the other working vacuum because we had a storm rolled through while I was in the middle of this. I did try to move the levers by hand but they were hooked up to the actuators so they weren't going to budge.

I planned on replacing the electric blend door actuator this weekend but discovered it's way cheaper to order this part online so I'm going to put that off for now. There's probably a good chance that the defroster door is stuck since this truck sat for maybe 2 years. I'll research that on the site. Thanks for the info and help!