While i was at the yard last week i noticed a s10 with the dash ripped out so i took a look at the hvac stuff. if you pull your hvac controls panel off you'll see some multicolored vacuum hoses connected. If its the same with early blazers look for the brown hose,and start fishing in the dash and see if its disconnected. the brown hose ran from the "coupling" at the controls,to another similar coupling then to the actuator where the big vent door is for the center vents. both mine,and my dads blazer has this same issue. We have learned to ignore it. lol

 

andrewo1991.... the heater-defrost door acuator is located in the open to the right of your gas pedal if you have the square body s10 blazer. the vent door actuator is right above it but you would have to atleast take the bottom panels off to get to it i think. i have an entire diagram for the whole vacume system...follow this link. let me know what you think.... https://blazerforum.com/forum/1st-ge...m-vents-67194/

to chris o15... im really wanting it to work correctly because i spent about $250 replacing the a/c compressor and dryer. so im kinda bummed that everything doesnt work correctly. maybe im ocd. idk. lol. but everyone keeps telling me i have a vacuum leak but idk. i dont hear any hissing anywhere under the hood or in the dash. onlything i can think is that the actual control module is messed up or an actuator is not working. and if it is the actuator is it the heater- defrost actuator stuck or the vent door actuator stuck closed or open. idk. any ideas. oh and the actuator for these things are hard to find. advanced orielly's and atuou zone type stores doesnt have em.

 

ok when you turn it to a different setting like from defrost then to the vents or another setting you SHOULD HEAR A HISS at the controls for a few seconds then stop. put your ear up to it. if you dont then there is a tiny plastic vacuum lline about a 1/8in in diamiter very small at the back passenger side of the intake plenum under the hood.there will be a main line that connects from the intake that goes into a tee. and from that tee there should be that plastic line not rubber. its really easy for them to pop off. if its connected sometimes they break off right at the firewall. if the hose is fine take the controls out of the dash its kinda tricky but doable. then pop the rubber hoses off the back of it. there all connected together so dont try to pull one off. the start the truck. is there vacuum comming out of the hoses? if there is then its the switch. if there is no vacuum then the line has broke somwhere in the dash which is highly unlikely.

 

Mine hisses constantly when its a settting that involves shutting the floor. Doesnt stop. I know where the vacuum line is from too, cause i disconnected it :-) and i plugged it off dont worry. Im gonna check for a leak at the diaphram but i think it may be the switch cause i hear it hissing from there and not my floor board.

 

bam999..... i will try that tomorrow when i get off work. but what you are saying sounds about right. i hope its the plastic tube behind the plenum. i found a new control on ebay for $40. idk if its new or used but i know a new one is over $100 and up to $200 depending on where you look. im going to go outside and listen for the hissing now though andrew01991.

 

ok so i went to the junkyard and ripped a dash out so i could see everything first-hand without touching mine. a new control unit is only $15. not too bad but what im concerned about is that the vacuum hoses that run from the control unit go back about 12 inches and is hooked up by a rubber clip to the vacuum lines that run throughout the dash. im worried that if my control unit is fine and i have a good conection to it at the control unit what are the chances that the rubber clip that connects to evrything else has come loose? the clip looks just like a plastic electrical clip but its just made of a clearish vinilla colored rubber.

 

aaaaah! it was the control unit. got another from that car i ripped apart yesterday and installed it in mine and yeah......works great. so to recap.... i spent $2 on a spark plug to fix the rough idle and $15 to fix the a/c through the vents problem. thank the Lord, im truly blessed!!! thought i was gonna have to shuck out hundreds and only spent 20 bucks!

 

cool. i was thinking that it would either be the controls or that plastic vacuum line. glad i could help

 

is it hard to replce the driver side motor mount on an s10 4x4 blazer? where is the best place to get access?

 

dont just keep posting your problems here. make a new thread. new post whatever. but yea its a pain to replace that mount cause everyting thats in the way has to come out and motor to be jacked up a bit. i got mine done for 50 bucks at a local shop. but just from lookin at it you have to remove the steering shaft and air box and some other little things to get access. jack it up and support with jackstands. take driver side tire off and go through the wheel well maby. good luck