A/C AC diagnosis list and description B4 Passat

000utback

Well-known member
Joined
Mar 12, 2010
Location
VA
TDI
96 Passat sedan; 03 Jetta sedan; 04 Jetta sedan
Somewhere I read a list of things to check when trouble-shooting AC. Doggone of course I can't find it now. It was, like, "check for voltage at this spot" "check resistance at this spot" " check this sensor". That's like a general request for guidance in finding the link I know I've seen before. This guy needs help.

Right now I have the dash open enough to check the climate control module. When I turn the heat control (center knob), the cable doesn't move, so there must be a broken plastic bit in there. Does the AC circuit have any interaction with the temperature knob position, or with the blend door positions? While I have it apart this far, now is the time to check any of that.

The back side of the temperature control knob has a white cube with gray/blue and brown wires connected to it. Wuzzat?

I will try to connect a stiff wire to the temperature control cable and manipulate it from outside the dash. This is not a show car. But something in here is inhibiting the AC from coming on, I'll have to work on it.
Sorry if a ramble. Any advice appreciated.
 

000utback

Well-known member
Joined
Mar 12, 2010
Location
VA
TDI
96 Passat sedan; 03 Jetta sedan; 04 Jetta sedan
okay, I did find an answer to one of my questions. the white cube on the back of the temperature control knob is a cover for the light tunnels.

The temperature gears move, but the lever underneath does not. Must be a broken connection between it and the gear. There are a couple pieces of flat arched copper bouncing around. Are there any electrical contacts associated with the rotating knob positions? Or are these parts of the broken lever system?
Blend door controls are working fine mechanically and I got the heat control cable out where I can reach it.
Still interested in a flow chart for checking AC components.
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
Grey / blue is always interior illumination wiring, more specifically I think it's rheostat controlled lighting.

The temperature and direction are cable controlled, the fan is the only thing electrically controlled, the recirculation door is vacuum control. If you have bits of fan control contacts floating around the controls are probably bad and should be replaced. Then again it could be that those contacts are for illumination too.

Fortunately those controls are replaced as a unit and I'd get a replacement use that.

Steve
 
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