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
6,945
1,598
223
Northern KY
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 :(
 
  • Sponsors (?)


Diagram courtesy of Tmoss & Stang&2birds
Mustang_AC_heat_vacuum_controls.gif


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
 

Attachments

  • Mustang_AC_heat_vacuum_controls.gif
    Mustang_AC_heat_vacuum_controls.gif
    17.8 KB · Views: 50
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?
 
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.