HVAC not changing modes.


So my 94 Mk8, the fan works and changes speeds, but only does Defrost regardless of what you choose. It's buttons are all cracked out too.

The 95 organ donor cars unit looks the same with good buttons, so I took it out to put in the 94. Judging from the assy, it uses vacuum to change modes.

Can anyone tell me where the main vacuum supply is, I have a shop manual in the car, but I am not around it right now, I did a search for like issues but didn't see any.

Look for the fitting on the intake manifold that has one large line and one small line on the tee fitting with the large line going to the brake booster. The small line coming off that tee fitting is the vacuum source for the EATC module. With loss of vacuum to the EATC, the defrost position is the default setting.