Diagnostic Test

WARNING: This page is about a different car, the 2005 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

1) CHECK (C221) A/C SWITCH SENSE CIRCUIT VOLTAGE AT A/C HEATER CONTROL C1 HARNESS CONNECTOR

Fig 1: Checking A/C Switch Sense Circuit Voltage At A/C Heater Control C1 Harness Connector
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the A/C Heater Control C1 harness connector.

Turn the ignition on.

Measure the voltage of the (C221) A/C Switch Sense circuit.

Is the voltage below 4.8 volts?

Yes
1. Go To step 2).
No
1. Replace the A/C Heater Control in accordance with the Service Information.
2. Perform BODY VERIFICATION TEST - VER 1 .
2) CHECK (C221) A/C SWITCH SENSE CIRCUIT FOR A SHORT TO GROUND

Fig 2: Checking A/C Switch Sense Circuit For Short To Ground
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the Instrument Cluster C3 harness connector.

Measure the resistance of the (C221) A/C Switch Sense circuit between ground and the A/C Heater Control C1 harness connector.

Is the resistance below 10K ohms?

Yes
1. Repair the (C221) A/C Switch Sense circuit for a short to ground.
2. Perform BODY VERIFICATION TEST - VER 1 .
No
1. Go To step 3).
3) CHECK (C221) A/C SWITCH SENSE CIRCUIT FOR AN OPEN

Fig 3: Checking A/C Switch Sense Circuit For Open
Courtesy of DAIMLERCHRYSLER CORP.

Measure the resistance of the (C221) A/C Switch Sense circuit between the A/C Heater Control C1 harness connector and the Instrument Cluster C3 harness connector.

Is the resistance below 5.0 ohms?

Yes
1. Replace the Instrument Cluster (CCN) in accordance with the Service Information.
2. Perform BODY VERIFICATION TEST - VER 1 .
No
1. Repair the (C221) A/C Switch Sense circuit for an open.
2. Perform BODY VERIFICATION TEST - VER 1 .