Pinpoint Test D: The Audio System Illumination Is Inoperative

WARNING: This page is about a different car, the 2006 Mercury Grand Marquis and 2006 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: Use the correct probe adaptor(s) when making measurements. Failure to use the correct probe adaptor(s) may damage the connector.

D1 CHECK CIRCUIT 484 (OG/BK) FOR AN OPEN
- Disconnect: Audio Unit C290a or C240.
- With the parking lamps on, rotate the instrument panel dimmer switch to the maximum brightness level.
- Measure the voltage between the audio unit C290a-3, circuit 484 (OG/BK), harness side and ground; or between the audio unit C240-1, circuit 484 (OG/BK), harness side and ground.
  
  Fig 1: Checking Circuit 484 (OG/BK) For An Open
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : GO to D2.

No : REPAIR the circuit in question. TEST the system for normal operation.
D2 CHECK CIRCUIT 57 (BK) OR 694 (BK/LG) FOR AN OPEN
- Measure the resistance between the audio unit C290a-1G, circuit 694 (BK/LG), harness side and ground; or between the audio unit C240-2, circuit 57 (BK), harness side and ground.
  
  Fig 2: Checking Circuit 57 (BK) Or 694 (BK/LG) For An Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : REMOVE the audio unit. REFER to INFORMATION AND ENTERTAINMENT SYSTEMS . SEND it to an authorized audio system repair facility. TEST the system for normal operation after repair.

No : REPAIR the circuit in question. TEST the system for normal operation.