System Check - HVAC System - Manual

Manual Air Conditioning System Check:

Heater And A/C Control Head Appears Inoperative:

This procedure provides an overall check of the Heating and Air Conditioning System.
Complete the test with the Engine idling and the temperature outside the vehicle at 60°F (16°C) or higher. Set English-Metric Switch to "ENGLISH."

^ If the Heater and A/C Control Head appears completely inoperative, perform Chart #1, "Heater and A/C Control Head Appears Inoperative."

TECH 1 DIAGNOSIS
Vehicle Preparation

^ Connect a jumper wire from the Heater and A/C Control Head Connector, terminal "4" or terminal "5", to the ALDL Connector, terminal "J". Insert the jumper through the back (wire entry side) of each connector.
^ Install the Tech 1 using the Body Systems Cartridge. When the Tech 1 asks for the model year, key in 1990 (not 1993).
^ Proceed with climate control diagnosis.

IMPORTANT: To prevent future data line communication problems, remove the jumper wire after diagnosis.