ok 1998 Blazer...A few days ago I heard a small vacuum leak coming from behind the dash, so I took off the cluster and I could see where the leak was coming from...The position control switch, I took off the vacuum cluster that is connected to the switch and noticed that there was suction coming from the black vacuum line only...I also noticed that when accelerating the suction goes away but when I let off the gas it returns...Is there supposed to be some other suction or air blowing out one of the other colored lines? I did get another actuator and plugged it in, and nothing changed...no matter what position the switch is in...it doesnt change anything....I dont think it is the switch upon inspection but thought I would ask you all for an opinion...Thanks

 

Black line is the vacuum supply line to the HVAC control head. The mode changes made by you to the control head direct vacuum to the appropriate vacuum actuators in the dash. Run a search for 'vacuum actuator' or something similar and you should come across the diagrams and logic tables for both the automatic and manual HVAC controls.

 

Thanks for the reply kyle, I am not sure what you mean...I did a search and all that came up was topic about the 4wd actuator...I did buy a new "mode actuator" and plugged in the electrical plug and that didnt help me...I am sorry could you explain more? Thanks

 

Heater issues - Help I just moved to Boston from Ar...

That should cover it for you.

 

Ok, so what part would you think I should replace? The schematic seems real confusing. I am pretty sure it is not the position switch...Thanks

*Combining Consecutive Posts*

I also dont have a problem with the temp setting..I get both hot and cold, just cant switch position.....


*EDIT by swartlkk* - Please use the edit feature to add additional information to your post if another member has yet to reply. Thanks!

 

I also dont have a problem with the temp setting..I get both hot and cold, just cant switch position.....

 

Well, do you have automatic climate control or manual?

 

I would assume I have manual as it is a ****...How can I tell?

 

If you had auto, you would set it to a temperature, not just a color (red/blue) and you would have an 'Auto' position for the mode and the fan.

So I would go through the logic chart, verifying that you have vacuum to the appropriate ports on the back of the control head when in the various modes. If that checks out, then I would inspect the lines to the individual actuators. You may need to disconnect the lines at each actuator as well.

 

Ok it's manual and no matter what position the switch is in, the only suction is coming from the black vacuum line....like I said the heat control works just not the position...sorry i am being such a pain....thanks