Reconnect the A/C pressure switch 2P connector. Disconnect the heater control panel connector A (14P). Turn the ignition switch ON (II). Measure the voltage between the No. 4 terminal of heater control panel connector A (14P) and body ground. HEATER CONTROL PANEL CONNECTOR A (14P) Is there battery voltage? YES - Check for loose wires or poor connections at heater control panel connector A (14P) and at the A/C pressure switch 2P connector. If the connections are good, substitute a known-good heater control panel and recheck. If the symptom/indication goes away, replace the original heater control panel. NO - Repair open in the wire between the heater control panel and the A/C pressure switch.

Make sure the A/C switch is OFF. Measure the voltage between the No. 9 terminal of under-dash fuse/relay box connector F (12P) and body ground with the under-dash fuse/relay box connectors connected. UNDER-DASH FUSE/RELAY BOX CONNECTOR F (12P) Wire side of female terminals Is there battery voltage? YES - Repair open in the wire between the under-dash fuse/relay box and the A/C pressure switch. NO - Refer to the multiplex control system (see page 22-268). Check for proper A/C system pressure. Is the pressure within specifications? YES - Replace the A/C pressure switch. NO - Repair the A/C pressure problem.