AC/Heater Control Problems...Help!

[Bottomlesspit]

Hi guys,
I am having some troubles...another in the long list...with the hvac control panel in my 92GT hatch.
The temp control knob has been a bit "stretchy" since we bought the car a few years ago. I mean when you twist it it would feel like it was attached to a rubber band. The knob would not turn smoothly, it would tense up..like winding up the rubber band, then let go and move, then do the same twisting it the other direction.
Coming home from work tonight I got the bright idea of twisting all the knobs to see if everything works correctly. As luck would have it, it got stuck on full Hot and I have had hot air coming in since then. Not good here in SW Texas! I have played with the temp knob and after fiddling with it I find that it now can spin all the way around! Full 360.
I have to be out of town until Sunday, but hope to pull the panel Sunday evening and take a good look.
I am not familiar with this particular control head, beyond pulling it out a slight bit when working on the dash
I'm hoping someone might be able to offer some pointers. Are there any adjustments that I can make to this unit?
Does this mean the unit is shot and has to be totally replaced?
Any replaceable parts?
It is definitely NOT the knob itself.
Any info, pointers, suggestions, steps, etc you can offer will be most appreciated. It's stuck on full hot and not fun to drive!
Thanks,
Ken
BTW: the blower speed works fine. The setting knob: AC, defrost, vent, etc also appears to cycle and work fine.

 

[Saleen0679]

Problem must be either the control or the cable unless something broke at the blend door. Maybe the cable got disconnected from the blend door. The cable is replaceable and has an initial adjustment before installation.

Here are some Ford instructions:

Temperature Control Cable

Removal

1.) Remove control assembly from instrument panel.
2.) Disengage temperature control cable from cable actuator on control assembly.
3.) Disconnect temperature cable from plenum temperature blend door crank arm and cable mounting bracket.
4.) Note cable routing and remove cable from vehicle.

Before Installation

1.) Insert the blade of a small pocket screwdriver into the wire end loop (crank arm end) of the control cable (Fig. 7).
2.) Grip the self-adjusting clip with pliers and slide it down the control wire (away from the end loop) approximately 25.4mm (1 inch).
3.) Install the cable assembly. Refer to Control Assembly and Temperature Control Cable Removal and Installation.
4.) Rapidly rotate the control knob to its fully warm position. This will position the self-adjusting clip.
5.) Check for proper control operation.

Temperature Control Cable

The temperature control cable is self-adjusting with the rapid rotation of the temperature control knob to its fully WARM position. To prevent kinking of the control cable wire, a preset adjustment should be made before attempting to perform the self-adjustment operation. The preset adjustment may be performed either in the vehicle, with the cable installed or before installation (Fig. 7).


Installation

1.) Check to ensure self-adjusting clip is at least 25.4mm (1 inch) from end loop of control cable. Refer to Adjustments.
2.) Route cable behind instrument panel and connect control cable to mounting bracket on plenum.
3.) Install self-adjusting clip on temperature blend door crank arm.
4.) Engage cable end with cable actuator on control assembly.
5.) Install control assembly in instrument panel.
6.) Turn temperature control knob all the way to the right (WARM) to position self-adjusting clip on control cable.
7.) Check temperature control knob for proper operation.
8.) Check system for proper operation.

After Installation

1.) Move the control lever to the COOL position.
2.) Hold the crank arm firmly in position, insert the blade of a small pocket screwdriver into the wire loop and pull the cable wire end through the self-adjusting clip until there is a space of approximately 25.4mm (1 inch) between the clip and the wire end loop (Fig. 7).
3.) Rapidly move the control knob to its fully warm position to position the self-adjusting clip.
4.) Check for proper control operation.

 

[jrichker]

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/

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

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

Computer, actuator & sensor wiring
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

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

Vacuum routing
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

 

[Bottomlesspit]

Hey, once again big thanks to you guys for the help. I'm taking all this info to the garage tomorrow and see what i can find. At least I have somewhere to start now. Good info, should help a lot.
Ken