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  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

Interior and Upholstery Unable to switch A/C controls

  • Thread starter Thread starter stangdrvr4life
  • Start date Start date Sep 29, 2019
S

stangdrvr4life

Member
May 8, 2005
16
1
13
Sep 29, 2019
#1
  • Sep 29, 2019
  • #1
So, after the previous fight with getting the car running, she's operating absolutely wonderful. HOWEVER....

Now I cannot change the settings for the climate control. I know normally if there's bad vacuum, it defaults to the defrost. That's just the thing. I replaced all the vacuum lines because I thought that was the problem, but it is also blowing out of the floor vents too. The only thing I can seem to control is the blower speed. Right now I don't appear to have heat either, but have yet to take a look at the heater core to identify that problem. It's still in the upper 80s here so AC is still a concern. There does not seem to be any positive detent on the mode selector switch, so I'm not entirely sure it's good (and finding a replacement seems impossible). Any one have any advice on some other things I should check?
 

jrichker

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Mar 10, 2000
27,512
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Dublin GA
Sep 29, 2019
#2
  • Sep 29, 2019
  • #2
Vacuum, Vacuum and more Vacuum. There are several vacuum servos that open and close the various doors that control airflow. Check the vacuum feed from the engine first and then check for vacuum at the vacuum servo when they are selected on the HVAC control panel.

The following are diagrams courtesy of Tmoss & Stang&2birds

Vacuum diagram 89-93 Mustangs


HVAC vacuum diagram


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.


TFI module wiring for 94-95 Mustang GT
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-IgnitionControlModule.gif

Complete computer, actuator & sensor wiring diagram for 94-95 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/94-95_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 88-90 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

5.0 wiring diagram for Fuel Injectors, Sensors, and Actuators
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

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

O2 sensor wiring harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangO2Harness.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 & pin out
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

Mustang 5.0 Lights and Radio schematic, by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxLights-Radio_diag.gif

87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92%20PowerWindowWiring.gif

93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif

T5 Cutaway showing T5 internal parts
http://www.veryuseful.com/mustang/tech/engine/images/5_Speed_Cutaway_Illustrated.jpg

Visual comparison of the Ford Fuel Injectors, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/Ford_Injector_Guide.jpg

Convertible top motor wiring http://www.veryuseful.com/mustang/tech/engine/images/mustang88VertTopMotorCkt.gif

Engine mounted fuel injector harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangEngineHarness.gif

Location of the TPS, IAB, and the 10-pin connectors on a 5.0, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/TPS_IAB_Pic.jpg

Starter circuit
http://forums.stangnet.com/attachment.php?attachmentid=21328&d=1080916057

Alternator diagram for 94-95 Mustangs.
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-Alt.gif
 

General karthief

wonder how much it would cost to ship you a pair
5 Year Member
Aug 25, 2016
27,848
10,528
203
polk county florida
Sep 29, 2019
#3
  • Sep 29, 2019
  • #3
Do you have vacuum at the switch?
that is the place to start
 
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