Hvac issue
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2nd Gear
Joined: Jun 2025
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Hvac issue
My 2003 has the dreaded hot air from the passenger vents when AC is running. I've checked some of the older threads on this site and have tried some things as were suggested. No luck so far. I disconnected the vacuum line coming from the intake manifold from the purple line to the HVAC vacuum block. When running, the line to the manifold holds at 20 1/2" of mercury. I pump up the vacuum on the purple line and it holds until I change modes on the control panel, then I lose vacuum. I assume that is normal. Could something in the ductwork be physically preventing cold air from coming through the passenger vents? Any help or suggestions will be appreciated!
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Pro
Joined: Dec 2014
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From: Cincinnati Ohio
The vacuum is for switching modes, defrost, vent, bi level, and floor. Are you able to change between these modes?
The temperature change is controlled electrically. With the engine running and warm and the mode in vent, as you change the temperature from all the way cold to full hot, does the air coming out of the vents get very very warm? If so, your temperature control probably works.
How do you know your a/c is working? With the a/c on and your hood up, feel the refrigerant lines; do both of the refrigerant lines feel cold?
The temperature change is controlled electrically. With the engine running and warm and the mode in vent, as you change the temperature from all the way cold to full hot, does the air coming out of the vents get very very warm? If so, your temperature control probably works.
How do you know your a/c is working? With the a/c on and your hood up, feel the refrigerant lines; do both of the refrigerant lines feel cold?
Pro
Joined: Dec 2014
Posts: 682
Likes: 275
From: Cincinnati Ohio
Do you have the automatic dual zone control head? If so:
One relatively easy way to confirm it is the air handling side would be to pinch the heater inlet rubber hose closed. That should prevent your heater from reheating the air to the passenger side. Without the heater reheating the cooled passenger side, the passenger side should now be cold air.
