The mode switch is vacuum controlled , do you know anything about vacuum controls , how to test vacuum circuits ? here is a factory diagnostic flow chart for what to test.
HVAC Air Delivery System Check
Step
Action
Yes
No
1
Start the engine.
Turn the blower motor fan ON and select an air outlet mode.
Does air flow out of the selected HVAC outlet ducts?
YES - Go to Step 3
NO - Go to Step 2
2
Did the customer concern mention that the air discharges out the correct ducts at first, but then changes during higher engine RPM?
YES - Go to Step 7
NO - Go to Step 3
3
With the engine running, cycle the HVAC controls through all the modes.
Does the air come out of the selected outlet ducts?
YES - Go to Step 18
NO - Go to Step 4
4
With the engine running, take a vacuum reading at the manifold vacuum port that supplies vacuum to the HVAC vacuum control assembly.
Is there engine vacuum?
YES - Go to Step 6
NO - Go to Step 5
5
Repair the no vacuum condition.
Is the repair complete?
YES -- Go to Step 18
--
6
Take a vacuum reading at the vacuum supply line at the HVAC vacuum control assembly.
Is the vacuum reading the same as the engine vacuum?
YES - Go to Step 11
NO - Go to Step 8
7
Disconnect the vacuum supply line from the HVAC vacuum control assembly.
With the vacuum gauge connected to the vacuum supply line, re-start the engine and turn the engine OFF.
Does the system lose vacuum after turning OFF the engine?
Go to Step 8
Go to Step 11
8
Inspect for leaking or collapsed vacuum lines between the engine manifold vacuum port and the HVAC vacuum control assembly.
Are the vacuum lines leaking?
Go to Step 9
Go to Step 10
9
Repair or replace the collapsed or leaking vacuum line.
Is the repair complete?
Go to Step 18
--
10
Replace the vacuum reservoir tank.
Is the repair complete?
Go to Step 18
--
11
Using an external vacuum source, apply vacuum to the appropriate vacuum line at the connector to the HVAC vacuum control assembly.
Does the actuator retract?
Go to Step 17
Go to Step 12
12
Inspect for leaking or collapsed vacuum lines between the actuator and the connector to the HVAC vacuum control assembly.
Are the vacuum lines leaking?
Go to Step 9
Go to Step 13
13
Disconnect the vacuum line from the actuator.
Apply an external vacuum source to the actuator.
Did the actuator retract?
Go to Step 14
Go to Step 16
14
With the actuator disconnected, inspect the door for binding.
Does the door move freely?
Go to Step 16
Go to Step 15
15
Repair the appropriate binding door.
Is the repair complete?
Go to Step 18
--
16
Replace the appropriate vacuum actuator.
Is the repair complete?
Go to Step 18
--
17
Replace the HVAC vacuum control assembly.
Is the repair complete?
Go to Step 18
--
18
Cycle the HVAC controls through all modes to verify proper operation.
Did you correct the condition?
System OK
--
SOURCE: 1998 Mustang - AC blows only through Defrost vents
You probably have a vacuum leak on the passenger side. its a small plastic hose some times they come unpluged from the engine. or brake.
SOURCE: no air, ac, heat out of in dash face vent
I changed my switch..on my dash...that controls the different settings. All settings work fine now.
SOURCE: Heat wont blow through heater or defroster vents
common problem, check under dash by the gas pedal if control arms are muving went selecting from ac to heat cuz this it is the control for the vents to go from ac to heat and to defrost.
SOURCE: ac vent problem
Damper/flap for driver's side is probably stuck. Try moving the selector from cold to hot several times. Also, move the recirc/outside air control if the previous doesn't work.
NO HEAT ON FLOOR VENTS
---------
As
per your problem mentioned. There are few solved help links to
troubleshoot these problems. Go through the list and Click the link below:----
http://whatisbyme.blogspot.in/2012/05/2000-toyota-avalon-no-heat-on-passenger.html
------------
------------
http://schematicsdiagram.blogspot.in/2012/02/heater-blows-cold.html
-----------
http://repairhelpcenter.blogspot.com/2012/01/hot-air-on-drivers-side-vents-only.html
--------------
-----------
http://technoanswers.blogspot.in/2012/04/1992-toyota-camry-ac-control-light.html
--------------
http://technoanswers.blogspot.in/2012/02/no-heatblower-blows-only-cold.html
----------
-------------
http://whoisbyme.blogspot.in/2012/06/2009-mercury-grand-marquis-ac-blows.html
-----------
http://schematicsdiagram.blogspot.in/2012/04/ac-not-blowing-through-vents-on-2007.html
----------
http://schematicsdiagram.blogspot.in/2012/04/passenger-side-temperature-is-warm-air.html
----------
These
will help.
Thanks.
As
per your problem mentioned. There are few solved help links to
troubleshoot these problems. Go through the list and Click the link below:----
------------
------------
http://schematicsdiagram.blogspot.in/2012/02/heater-blows-cold.html
-----------
http://repairhelpcenter.blogspot.com/2012/01/hot-air-on-drivers-side-vents-only.html
--------------
-----------
http://technoanswers.blogspot.in/2012/04/1992-toyota-camry-ac-control-light.html
--------------
These will help.
Thanks.
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