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Home >> Audi >> 2010 >> A4 2.0T >> Repair and Diagnosis >> External Pages >> Different car >> Section 1031 (Climate Control System - General Information (2 Of 2)) >> Diagnosis And Testing >> Climate Control System >> Pinpoint Test(s) >> Pinpoint Test F : Insufficient, Erratic Or No Heat >> Pinpoint Test F : Insufficient, Erratic Or No Heat

Pinpoint Test F : Insufficient, Erratic Or No Heat

WARNING: This page is about a different car, the 2018 Lincoln Navigator. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Restriction of air flow through the radiator or Air Conditioning (A/C) condenser by an external obstruction such as leaves or cardboard can cause erratic operation.
NOTE: Missing or broken engine coolant hose check valve or incorrect orientation of check valve (if equipped) can cause poor heater performance at idle.

  1. F1 CHECK FOR CORRECT ENGINE COOLANT LEVEL

    • Ignition OFF.

    • Visually check the engine coolant level in the degas bottle.

    Is the engine coolant at the correct level as indicated on the engine coolant recovery reservoir? 

    Yes  GO to  F2
    No  DIAGNOSE the engine for loss of coolant. Refer to the appropriate Engine article for the procedure.

  2. F2 CHECK THE ENGINE COOLANT VENT HOSE CHECK VALVE

    NOTE: Do not apply more than 96 kPa (14 psi) compressed air to the vent hose check valve, or the valve may be damaged.

    • Remove the upper radiator hose.

    • Using a light, look inside the end of the vent hose that connects to the degas bottle. A check valve should be installed approximately 100 mm (3.94 in) from the end of the hose.

    • Using hose pinch pliers, clamp the upper radiator hose near the degas bottle hose connection on the side of the upper radiator hose that leads to the radiator.

    • NOTE: Use shop towels to seal the end of the upper radiator hose where regulated compressed air is applied.

      Using regulated compressed air, confirm air flows freely from the upper radiator hose end to the degas bottle end.

    • Using regulated compressed air, confirm air does not flow from the degas bottle end to the upper radiator hose end.

    Is the check valve installed in the vent hose and does air flow through in one direction and not the other? 

    Yes  GO to  F3
    No  INSTALL a new upper radiator hose. Refer to the appropriate Engine article for the procedure.

  3. F3 CHECK FOR COOLANT FLOW TO THE HEATER CORE

    • Run the engine until it reaches normal operating temperature. Select the floor position on the HVAC controls. Set the temperature control to full warm and the blower to the lowest setting.

    • Increase engine speed to 3, 500 RPM and hold for 30 seconds.

    • Allow the engine to idle for 30 seconds.

    • Using a suitable temperature measuring device, check the heater core inlet hose to see if it is hot.

    Is the heater core inlet hose temperature above 66°C (150°F)? 

    Yes  GO to  F4
    No  If equipped with a cabin heater coolant pump, DIAGNOSE for the cabin coolant pump causing a possible restriction of flow to the heater core. GO to Pinpoint Test S 
    If not equipped with a cabin heater coolant pump, DIAGNOSE the engine does not reach normal operating temperature. Refer to the appropriate Engine article for the procedure.

  4. F4 CHECK FOR A PLUGGED OR RESTRICTED HEATER CORE

    • Using a suitable temperature measuring device, measure the heater core outlet hose temperature.

    Is the heater core outlet hose temperature similar to the inlet hose temperature (within approximately 6-17°C [10-30°F])? 

    Yes  DIAGNOSE for a temperature door actuator not operating correctly.For inadequate driver side temperature, GO to Pinpoint Test I  For inadequate passenger side temperature, GO to Pinpoint Test J 
    No  INSTALL a new heater core. REFER to: Heater Core .
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