HVAC vacuum diagram

CARPETMAN1759

MEMBER
2002 CHEVROLET S-10
4.3L
V6
4WD
AUTOMATIC
115,000 MILES

Need vacuum hose diagram for under the dash. Fixed all parts and hoses under the hood and I have vacuum going into the firewall, but no vacuum inside. I have a new selector switch and also fixed a loose hose behind glove box. Will be replacing radio so I will have the dash all apart. Would like to follow the vacuum lines to fix the problem. All of the air comes out the front air vents. One of the plungers that controls that is behind the glove-box door and that part is new and I am not getting no vacuum to that part at all. Thanks for any help someone can give me.

5 Replies

HMAC300

MECHANIC
48,601 POSTS

Hoses should be color coded so easy to follow if no color pretty much self explanatory. See picture.

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Monday, July 29th, 2019 AT 8:31 PM

CARPETMAN1759

MEMBER
81 POSTS

So I take it that the small hard plastic black hose goes through the firewall and attaches to the selector switch and then gets routed to all the different actuators. Thanks again HMAC300! I should be able to track down the leak or the blockage hopefully. I will let you know what I find.

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Monday, July 29th, 2019 AT 8:31 PM

HMAC300

MECHANIC
48,601 POSTS

A lot of times it is the vacuum motor or the vacuum switch on the control itself.

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Monday, July 29th, 2019 AT 8:31 PM

CARPETMAN1759

MEMBER
81 POSTS

The switch is new but I have another one and a couple of used ones that I will change out with, so I can rule out the switch. But the vacuum motor? I thought the only motor was the temperature blend door. I only want to take this thing apart one time so I want to check everything I can. I will check all vacuum actuators and check to see if any doors stick. What else should I look at? The winter is coming and I hate hot air blowing at me. Will not come out the defrost or floor.

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+1

Monday, July 29th, 2019 AT 8:31 PM

HMAC300

MECHANIC
48,601 POSTS

Vacuum motors are the things that use vacuum to operate the doors. Nothing to worry about. The temperature actuator is electric. You should check the mode and defrost actuators (motors) you may just have a bad line or line off.