With HVAC System - Automatic

IMPORTANT: If Heater and A/C Control Head and/or Programmer appear completely inoperative, refer to A/C System Check diagnosis chart before proceeding.
Diagnosis for this system is based on diagnostic codes stored in the Heater and A/C Control Head. When a code has been stored, the MODE Indicator (LED) of the current mode will flash. Three dashes will be displayed on the Heater and A/C Control Head if the A/C Programmer fails. For code diagnostics, refer to A/C and Heating Section.

1. Air flow out of the Defroster Duct only is an indication of no vacuum present at the Heater and A/C Programmer.
2. If the Air Mix Door is disturbed for any reason, you must disconnect the Battery or the Heater and A/C Programmer momentarily to start the calibration sequence. During the calibration process the Blower Motor will not operate for approximately 1-1/2 minutes.
3. After an Outside Temperature Sensor has been changed or is open, the external temperature will read -50°F and Code 03 will be set until the vehicle has been driven over 25 mph for three minutes.
4. The Outside Air Temperature Display will not increase until vehicle is driven over 25 mph for three minutes.
5. If a low Freon fault Code 09 is set, the A/C Compressor will not operate. To reset this code, disconnect Battery or pull the A/C PROG Fuse, then reconnect.
6. Check manifold vacuum at the Black hose from the Engine on the Vacuum Tank.
^ If vacuum is not present, check the hose back to the Engine Vacuum Source.
^ If vacuum is present, check for vacuum at the Black hose at the Heater and A/C Control Head. If there is no vacuum at the Heater and A/C Control Head, replace the Vacuum Tank.
7. Check that the vacuum hoses from the Heater and A/C Programmer to the Vacuum Actuators are connected and in good condition.

^ Refer to the A/C System Check for a guide to normal operation and diagnostic references.
^ Check for a broken (or partially broken) wire inside of the insulation which could cause system failure but prove "GOOD" in a continuity/voltage check.
^ Check for proper installation of aftermarket electronic equipment which may affect the integrity of other systems.

SYSTEM DIAGNOSIS

IMPORTANT: If Heater and A/C Control Head and/or Programmer appear completely inoperative, refer to A/C System Check, and perform Chart #2 before proceeding.

Diagnosis for this system is based on diagnostic codes stored in the Heater and A/C Control Head. When a code has been stored, the MODE Indicator (LED) of the current mode will flash. Three dashes will be displayed on the Heater and A/C Control Head if the A/C Programmer fails.