Pinpoint Test D: The Climate Control Illumination Is Inoperative

D1 VERIFY THE CLIMATE CONTROL ILLUMINATION
- Place the headlamp switch in the PARK position.
- Rotate the dimmer switch to the maximum brightness position.
- Do the climate control, transmission range selector lever, and audio unit illumination operate correctly?
1. Yes : The system is OK.
2. No : If the climate control unit is inoperative, GO to D2.
  If the climate control, transmission range selector lever, and audio unit are inoperative, GO to PINPOINT TEST A .
D2 CHECK CIRCUIT 434 (LB/BK) FOR VOLTAGE
- Place the headlamp switch in the OFF position.
- Disconnect: Dual Automatic Temperature Control (DATC) C228a.
- Place the headlamp switch in the PARK position.
- Measure the voltage between the DATC C228a-16, circuit 434 (LB/BK), harness side and ground.
  
  Fig 1: Measuring Voltage Between DATC C228a-16, Circuit 434 (LB/BK), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
1. Yes : GO to D3.
2. No : REPAIR the circuit. TEST the system for normal operation.
D3 CHECK CIRCUIT 1203 (BK/LB) FOR AN OPEN
- Place the headlamp switch in the OFF position.
- Disconnect: DATC C228b.
- Measure the resistance between the DATC C228b-2, circuit 1203 (BK/LB), harness side and ground.
  
  Fig 2: Measuring Resistance Between DATC C228b-2, Circuit 1203 (BK/LB), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
1. Yes : INSTALL a new DATC unit. REFER to CONTROL COMPONENTS .
2. No : REPAIR the circuit. TEST the system for normal operation.