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| Black thing
attached to the underside of the hood that looks like a bunch of tennis
balls |
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The black thing is a vacuum reservoir for the A/C system since the system works via vacuum
pressure rather than via cables.
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| Center
vent air |
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The stock, factory-installed HVAC system from
1982 to 1993 is built to allow both cooled and heated air to exit the
center vent. See the factory diagram below.
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| Only cold/cool air comes through the side vents |
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Heated air is simply not routed through that part of the system.
Click here
for a diagram.
See
the How-To page for a guide on how to alter the vents to enable heated air
to exit them.
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| No air comes
out of the center vent and/or floor vent |
|
The HVAC system is composed of these main
components: vacuum hoses/tubes, vacuum tank, vacuum distributor, vacuum
servos which operate vent flaps and a vacuum check valve. If any of these
components fail, air flow will be affected. It is highly recommended that
you purchase a vacuum pump to test the system and its components. First,
remove the check valve and apply vacuum to the port on the "motor" side of
the check valve while a finger plugs the opposite port. If it fails to hold
vacuum it may be faulty. If it holds vacuum, apply vacuum to the center
vent/defrost servo (remove the hose from the distributor); if it doesn't
hold vacuum or open the center vent flap, this is the cause of the problem.
If it opens the flap and holds vacuum, apply vacuum to the vac reservoir
port on the vacuum distributor; if it fails to hold vacuum, this is the
cause of the problem. Lastly, check all vacuum lines and connections for
possible leaks; replace as needed. (Removing the radio and the dash bezel
allow access to the vacuum distributor and servos for testing.)
Click here for the HVAC vacuum diagram
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| Only heated air or no heat exits the center vents |
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According to the Bentley manual there most
likely is a vacuum leak somewhere in the system; or there is a faulty servo
(inside the dash) or air distributor (inside the dash under the radio, right
side). This part of the HVAC system uses a cable; therefore, it is also
possible that the heater control cable is binding or has come detached from
the control valve located in the engine bay near the brake fluid reservoir.
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| Fan blower works
on only one or two settings, or not at all |
|
The fan motor is worn out, the fan switch is
faulty, wires are faulty, or the resistor is faulty. Consult the Bentley
Service Manual for repair information. Also see
this thread and/or
this thread on VWvortex for further information. If the blower fan does
not work on speed 4 but works on speeds 1, 2 and 3, and the A/C works on all
settings, the culprit is most likely a faulty A/C relay.
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