A/C Switch Signal

Plug system checker harness between ECU and connector. Start engine. Turn blower switch and A/C switches "ON". Ensure compressor and condenser cooling fan are working. Connect voltmeter positive probe to terminal B8 (Blue/Red wire) and negative probe to terminal A18 (Black/Red wire). Voltage should be zero to 3 volts. If voltage is not within specification, check for open circuit in Blue/Red wire between A/C diode connector and ECU.

NOTE: Voltage should be above 9 volts, if compressor or condenser cooling fan stops when power is cut-off by pressure switch or thermostat.