A/C Vacuum Switching Valve
- When A/C is operated, ECM operates A/C Solenoid Vacuum (SV) valve to supply by-pass air to increase engine idle speed. A/C SV valve is mounted on firewall, right of ignition coil. See Fig 1
. Install Tech 1 scan tester. Start and run engine. Turn A/C on and blower speed selector switch to any position except OFF. If engine speed increases slightly with A/C operation, A/C SV valve system is functioning normally.
- If engine speed does not increase, backprobe A/C SV valve connector from cavity No. 2 to ground using a fused jumper. If engine speed increases, check for an open in Blue/Red wire. If wiring is okay, replace A/C amplifier. If engine speed does not increase, check for an open in Yellow wire. If wiring is okay, replace A/C SV valve.
Courtesy of GENERAL MOTORS CORP.