Air conditioner

Hi and thanks for using 2CarPros. Com.

Based on your description, it sounds like the cable to the blend air door is broken or the door itself. The heater and optional air conditioner are blend-air type systems. In a blend-air system, a blend-air door controls the amount of unconditioned air (or cooled air from the evaporator on models with air conditioning) that is allowed to flow through, or around, the heater core. A temperature control knob on the heater-A/C control panel determines the discharge air temperature by moving a cable, which operates the blend-air door. This allows an almost immediate manual control of the output air temperature of the system.

What I need you to check is if the cable or door are broken. The components are located under the dash and a pain to get to, but it can be done. I have attached pictures of the system so you know what you are looking for.

According to alldata, here are the causes of not being able to control the temperature.

If temperature cannot be adjusted with the TEMP lever on the control panel, the following could require service:
1. Blend-air door binding.
2. Faulty blend-air door cable.
3. Improper engine coolant temperature.
4. Faulty Instrument Pan4 Control.

Since your vehicle works when the brake is applied, I feel strongly that the door is loose and moving into the open position and allowing cool air to enter the vehicle.

Let me know if this helps or if you have other questions.

Take care,
Joe