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I need to clarify whether my car has an electric mode actuator or a vacuum control mode actuator. The blend is fine but the air comes out everywhere. I think that there is more cold air coming out the defroster vents than from the front ducts and in Florida during the summer, that just ain't going to cut it. Anyone who has first hand knowledge would be appreciated.
The C5 uses a vacuum mode control actuator for both the manual single zone HVAC and the electronic Dual zone HVAC.
The culprit if you are having air come out all vents is the small vacuum line on the back of the intake manifold. It is either disconnected or the hard plastic vacuum line from the manifold to the passenger front fender area is damaged.
Here is a diagram showing how electrical motors are used to operate the doors for cold/ hot air and showing how electrical operated solonoids use vacuum to move the different vent doors
Not necessarily needed, but just to clarify for the OP, air direction is dictated with actuators using vacuum (which open/close plastic flaps on the HVAC box) , but said vacuum actuators are controlled electronically by the block shown in the diagram.
i would say it’s worth locating the vacuum electronic valve block as a secondary place to check things out (especially if you can’t see the black vac line under the hood). This part (the valve block) is up behind the glove box. You should see yellow red and blue coloured plastic lines going to it, the black line too, it being the one that comes through from the engine bay, to feed the block with vacuum.
indeed it may have detached under the hood. I never found it easily myself under the hood because most of its route is taped in to wiring harness.
if you can see the black line is connected ok to the block under the dash 1. Your problem is likely under the hood but 2. You could pull the black line, start the car and listen or feel (by placing finger over line) for vacuum at it here.
Last edited by silver50; May 15, 2021 at 01:10 PM.
2002 C5 HVAC mode problem
