Help me fix my HVAC

85_SS_302_Coupe

it sucks (I know) to be on the receiving end

15 Year Member

Nov 11, 2003

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Northern KY

Dec 8, 2007

#1

• Dec 8, 2007

• #1

The heating/AC (well i don't have AC anymore..) is one of those things i've never played with and know nothing about...so i need help.


Basically over the course of owning this car i've lost my adjustments...the flloor/panel/mix/defrost adjustments with the heat...i don't have anything except defrost now no matter what i move the switch to. I'm pretty sure it's some kind of vacuum issue but i have no idea where to to begin.


Any help? I'd like to have more than defrost

 

jrichker

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Dublin GA

Dec 8, 2007

#2

• Dec 8, 2007

• #2

Diagram courtesy of Tmoss & Stang&2birds


See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

 

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• Mustang_AC_heat_vacuum_controls.gif

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Santeeford

New Member

Sep 12, 2006

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2

San Diego

Dec 8, 2007

#3

• Dec 8, 2007

• #3

Check the vacuum bridge on the driver side of the engine compartment on the firewall. There is a line that is labeled HVAC. Check it for breaks all the way to the other end

 

85_SS_302_Coupe

it sucks (I know) to be on the receiving end

15 Year Member

Nov 11, 2003

6,945

1,598

223

Northern KY

Dec 8, 2007

#4

• Dec 8, 2007

• #4

jrichker, how close do you think that diagram is to my '85? Since my controlls are different (i only have the 3 up/down slider switches, not the knobs)?


Santeeford, where does that line go to?

 

tbovee

Member

May 22, 2006

129

0

17

Fredericksburg Va

Dec 9, 2007

#5

• Dec 9, 2007

• #5

IIRC the vacuum line routing is pretty close. They usually default to defrost when they loose vacuum. I'd check a lone vac hose going under or very near the heater core coolant hoses and see if its hooked up of leaking.

 

tmoss

Gettin Wired

Founding Member

Jun 28, 2001

7,153

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128

Saint Louis, MO

Dec 10, 2007

#6

• Dec 10, 2007

• #6

the yellow hose sometimes gets disconneccted if the Heating/Cooling panel has been removed - the connection to the vacuum motor is just a push-on connection.