Engine Speed Dips When A/C Is Switched on
ENGINE SPEED DIPS WHEN A/C IS SWITCHED ONConditions for Fault Tracing:
^ No DTCs present.
^ Engine hot.
^ Fault is permanent.
Fault sources
^ Open-circuit in signal lead from A/C compressor.
^ Faulty Idle Air Control (IAC) Valve.
TESTING PROCEDURE
Checking A/C Compressor Signal
^ START engine and allow to idle.
^ Switch ON A/C.
^ Select fan speed 1.
^ Display and read A/C compressor status.
If A/C compressor is ON:
- Proceed to: Checking IAC Valve Connector.
If A/C compressor is OFF:
- Proceed to: Checking Signal Lead, section below.
Checking IAC Valve Connector
^ Clean and grease IAC valve connector.
^ Check if engine speed still dips.
If speed dips:
- Try with new IAC valve.
Checking Signal Lead
^ Switch OFF ignition.
^ Connect test box to MFI system and check ground terminals.
^ Plug MFI module into test box adapter.
^ Switch ON A/C.
^ Select fan speed 1.
^ START engine.
^ Connect voltmeter across #25 (MFI A25) and #20 (MFI A20) on test box.
Instrument should indicate battery voltage when compressor runs.
If reading is correct:
- Speed dip is due to contact resistance in MFI Control Module connector.
- Clean and grease connector.
If reading is incorrect:
- Check lead between MFI module A25 and pressostat connector (7/53) terminal 2 for open-circuit.