Pinpoint Test F: The Defrost System Is Inoperative: Testing

WARNING: This page is about a different car, the 2005 Mercury Montego, 2005 Ford Freestyle, and 2005 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.

F1 CHECK THE REAR DEFROST INDICATOR LAMP
- Key in ON position.
- Turn the rear defroster ON.
- Does the rear defrost indicator lamp illuminate?
- Yes : GO to F3.
- No : GO to F2.
F2 CHECK FOR POWER TO THE SJB HEATED BACKLIGHT CIRCUIT
- Disconnect: SJB C2280a.
- Key in ON position.
- Measure the voltage between SJB C2280a-4, circuit 1846 (GY/LB), harness side and ground.
  
  Fig 1: Checking For Power To SJB Heated Backlight Circuit
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes : GO to F3.
- No : REPAIR the circuit. TEST the system for normal operation.
F3 CHECK THE SJB OUTPUT
- Key in OFF position.
- Connect: SJB C2280a.
- Disconnect: Heated Backlight Power C396.
- Key in ON position.
- Turn the rear defroster ON. Measure the voltage between rear window defrost grid power C402a, circuit 186 (BN/LB) and ground.
  
  Fig 2: Checking SJB Output
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes : GO to F4.
- No : GO to F5.
F4 CHECK THE REAR WINDOW DEFROST GRID GROUND
- Key in OFF position.
- Disconnect: Heated Backlight Ground C397.
- Measure the resistance between rear window defrost grid ground C402b, circuit 1205 (BK) and ground.
  
  Fig 3: Checking Rear Window Defrost Grid Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : GO to F5.
- No : REPAIR the rear window defrost grid or INSTALL a new rear window or liftgate window glass. REFER to WINDOW GRID WIRE REPAIR , WINDOW GLASS - REAR , WINDOW GLASS - LIFTGATE . TEST the system for normal operation.
F5 CHECK CIRCUIT 186 (BN/LB) FOR AN OPEN
- Key in ON position.
- Measure the resistance between heated backlight grid C396-1, circuit 186 (BN/LB), harness side and SJB C2280e-32, circuit 186 (BN/LB), harness side.
  
  Fig 4: Checking Circuit 186 (BN/LB) For An Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : GO to F6.
- No : REPAIR the circuit. TEST the system for normal operation.
F6 CHECK THE SJB HEATED BACKLIGHT RELAY PID
- Monitor the SJB heated backlight PID while triggering the SJB active command heated backlight relay.
- Does the SJB heated backlight relay PID value agree with the command mode?
- Yes : GO to F7.
- No : INSTALL a new SJB. TEST the system for normal operation
F7 CHECK CIRCUIT 1426 (PK) AND 1427 (TN/LB) FOR AN OPEN
- Key in OFF position.
- Disconnect: EATC C228a or EMTC C294a.
- Disconnect: SJB C2280b and C2280d.
- For manual climate control, measure the resistance between SJB C2280d-27, circuit 1426 (PK), harness side and EMTC module C294a-10, circuit 1426 (PK), harness side; and between SJB C2280b-25, circuit 1427 (TN/LB), harness side, and EMTC module C294a-4, circuit 1427 (TN/LB), harness side.
  
  Fig 5: Measuring Resistance Between SJB C2280D-27, Circuit 1426 (PK) And EMTC Module C294A-10, Circuit 1426 (PK) And Between SJB C2280B-25, Circuit 1427 (TN/LB) And EMTC Module C294A-4, Circuit 1427 (TN/LB)
  Courtesy of FORD MOTOR CO.
- For automatic climate control, measure the resistance between SJB C2280d-27, circuit 1426 (PK), harness side and EATC module C228a-10, circuit 1426 (PK), harness side; and between SJB C2280b-25, circuit 1427 (TN/LB), harness side, and EATC module C228a-4, circuit 1427 (TN/LB), harness side.
  
  Fig 6: Measuring Resistance Between SJB C2280D-27, Circuit 1426 (PK), Harness Side And EATC Module C228A-10, Circuit 1426 (PK) And Between SJB C2280B-25, Circuit 1427 (TN/LB) And EATC Module C228A-4, Circuit 1427 (TN/LB)
  Courtesy of FORD MOTOR CO.
- Are all resistances less than 5 ohms?
- Yes : INSTALL a new EATC or EMTC module. REFER to AIR DISTRIBUTION & FILTERING . TEST the system for normal operation.
- No : REPAIR the circuit(s). TEST the system for normal operation