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Pinpoint Test H: Insufficient, Erratic, Or No Heat

WARNING: This page is about a different car, the 2004 Lincoln LS. However, it is still accessible from the selected car via links, so may be relevant.
  1. H1 CHECK FOR CORRECT COOLANT LEVEL 
    • Key in OFF position.
    • Check the engine coolant level with the engine at cold and hot temperatures.
    • Is the engine coolant at the correct level (both cold and hot)? 
      1. Yes  : GO to  H4.
      2. No  : GO to H2.
  2. H2 CHECK THE ENGINE COOLING SYSTEM FOR LEAKS 
    WARNING: Never remove the pressure relief cap under any condition while the engine is operating. Failure to follow these instructions can result in damage to the cooling system or engine, or can result in personal injury. To avoid having scalding hot coolant or steam blow out of the cooling system, use extreme care when removing the pressure relief cap from a hot degas bottle. Wait until the engine has cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly one turn (counterclockwise). Step back while the pressure is released from the cooling system. When certain all the pressure has been released, use the cloth to remove the pressure relief cap.
    • Fill and bleed the engine cooling system.
    • Pressure check the engine cooling system, including the pressure relief cap.
    • Does the engine cooling system, including the pressure relief cap, hold pressure? 
      1. Yes  : GO to H3.
      2. No  : REPAIR the engine cooling system leak. TEST the system for normal operation.
  3. H3 VERIFY THE FAULT WAS A LOW ENGINE COOLANT LEVEL 
    NOTE: When carrying out this test step, allow time for the system to respond.
    • With the engine at normal operating temperature, set the DATC module driver and passenger side temperature settings to full hot (32°C [90°F]) and note the discharge air temperature.
    • Is the discharge air temperature at full hot? 
      1. Yes  : Test is complete.
      2. No  : GO to H4.
  4. H4 BLEED THE ENGINE COOLING SYSTEM 
    WARNING: Never remove the pressure relief cap under any condition while the engine is operating. Failure to follow these instructions can result in damage to the cooling system or engine, or can result in personal injury. To avoid having scalding hot coolant or steam blow out of the cooling system, use extreme care when removing the pressure relief cap from a hot degas bottle. Wait until the engine has cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly one turn (counterclockwise). Step back while the pressure is released from the cooling system. When certain all the pressure has been released, use the cloth to remove the pressure relief cap. NOTE: When carrying out this test step, allow time for the system to respond.
    • Bleed the engine cooling system.
    • With the engine at normal operating temperature, set the DATC module driver and passenger side temperature settings to full hot (32°C [90 °F]) and note the discharge air temperature.
    • Is the discharge air temperature at full hot? 
      1. Yes  : Test is complete.
      2. No  : GO to H5.
  5. H5 CHECK FOR HOT COOLANT AT THE HEATER CORE INLET HOSES 
    WARNING: The heater core inlet hoses will become too hot to handle and can cause serious burns if the system is working correctly. Failure to follow these instructions can result in personal injury.
    • Key in ON position.
    • With the engine running, carefully feel both heater core inlet hoses.
      Fig 1: Identifying Heater Core Inlet Hoses
      G03202244Courtesy of FORD MOTOR CO.
    • Are both heater core inlet hoses too hot to handle? 
      1. Yes  : CARRY OUT the heater core component test. REFER to HEATER CORE  under Component Tests in this section to determine whether a plugged or partially plugged condition exists.
      2. No  : GO to H6.
  6. H6 CHECK THE COOLANT CONTROL VALVE INLET HOSE 
    WARNING: The coolant control valve inlet hose will become too hot to handle and can cause serious burns if the system is working correctly. Failure to follow these instructions can result in personal injury.
    • Carefully feel both heater core inlet hoses.
    • Is the coolant control valve inlet hose too hot to handle? 
      1. Yes  : GO to H7.
      2. No  : INSTALL a new thermostat. TEST the system for normal operation.
  7. H7 CHECK DATC DTCS 
    • Check the DATC for DTCs.
    • Is DTC B2798 or B2800 present? 
      1. Yes  : GO to  H10.
      2. No  : GO to H8.
  8. H8 CHECK CIRCUITS 91S-FB4 (BN/GN) AND 91S-FB3 (BN/BU) FOR GROUND 
    • Key in OFF position.
    • Disconnect: Coolant Control Valve C1034.
    • Key in ON position.
    • Set the DATC module driver and passenger side temperature settings to full hot.
    • Measure the voltage between coolant control valve C1034-2, circuit 30-FB3 (RD/OG) and:
      • Coolant control valve C1034-1, circuit 91S-FB4 (BN/GN).
      • Coolant control valve C1034-3, circuit 91S-FB3 (BN/BU).
        Fig 2: Measuring Voltage Between Coolant Control Valve Circuits
        G03202245Courtesy of FORD MOTOR CO.
    • Is voltage present? 
      1. Yes  : GO to H9.
      2. No  : INSTALL a new coolant control valve. TEST the system for normal operation.
  9. H9 CHECK CIRCUITS 91S-FB4 (BN/GN) AND 91S-FB3 (BN/BU) FOR A SHORT TOGETHER 
    • Key in OFF position.
    • Disconnect: DATC Module C228b.
    • Measure the resistance between coolant control valve C1034-1, circuit 91S-FB4 (BN/GN) and C1034-3, circuit 91S-FB3 (BN/BU).
      Fig 3: Measuring Resistance Between Coolant Control Valve Circuits
      G03202246Courtesy of FORD MOTOR CO.
    • Is the resistance greater than 10,000 ohms? 
      1. Yes  : INSTALL a new DATC module. TEST the system for normal operation.
      2. No  : REPAIR circuit 91S-FB4 (BN/GN) for a short to circuit 91S-FB3 (BN/BU). TEST the system for normal operation.
  10. H10 CHECK CIRCUITS 91S-FB4 (BN/GN) AND 91S-FB3 (BN/BU) FOR A SHORT TO GROUND 
    • Key in OFF position.
    • Disconnect: DATC Module C228b.
    • Disconnect: Coolant Control Valve C1034.
    • Measure the resistance between ground and:
      • Coolant control valve C1034-1, circuit 91S-FB4 (BN/GN).
      • Coolant control valve C1034-3, circuit 91S-FB3 (BN/BU).
      Fig 4: Measuring Resistance Between Ground And Coolant Control Valve Circuit
      G03202247Courtesy of FORD MOTOR CO.
    • Are the resistances greater than 10,000 ohms? 
      1. Yes  : INSTALL a new DATC module. TEST the system for normal operation.
      2. No  : REPAIR circuit 91S-FB4 (BN/GN) or circuit 91S-FB3 (BN/BU) for a short to ground. TEST the system for normal operation.
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