Engine Speed Dips When A/C Is Switched On

FAULT TRACING INFORMATION

Conditions
^ DTCs absent.
^ Engine warm.
^ Fault permanent.

Fault Sources
^ Break in signal lead from A/C compressor.
^ Defective Idle Air Control (IAC) Valve.

TESTING PROCEDURE





Check A/C Compressor Signal
^ START engine and allow to idle.
^ A/C ON.
^ Blower ON.
^ Read off status for A/C compressor with compressor running.

If status for A/C compressor reads "ON":
- Proceed to: Check IAC Valve Connector, section below.
If status for A/C compressor reads "OFF":
- Proceed to: Check Signal Lead A/C Compressor, section below.

Check IAC Valve Connector
^ Clean and grease ECMs and IAC valve connector.
^ Check whether engine still slows.

If engine does not slow:
- Source of fault is bad contact in ECM and IAC valve connector.
If engine still slows:
- Test with a new IAC valve.





Check Signal Lead A/C Compressor
^ Ignition OFF.
^ Connect breakout box and check control points.
^ Connect ECM.
^ A/C ON.
^ Blower ON.
^ START engine.
^ Connect a voltmeter between #40 and #19 on breakout box.

With compressor running, voltmeter should read battery voltage.

If value OK:
- Source of slowing is contact resistance in ECM connector. Clean and grease ECM connector.
If value differs:
- Check lead between ECM #40 and A/C relay for break.