Fault profiles for the independent heating

Fault profiles for the independent heating

This document provides information on known fault profiles in the independent heating. The following fault profiles are described:

• Independent / auxiliary heating unit does not start
  - The independent / auxiliary heating unit shuts down after one or a number of start attempts (combustion-air fan audible, then switches off)
  
• Information on possible fault code memory entries in the control unit of the independent heating
  

If a fault is determined in the independent / auxiliary heating unit, the control unit is locked. Information of how to unlock the independent / auxiliary heating unit can be found at the end of this document.

Independent / auxiliary heating unit does not start

If the independent / auxiliary heating unit does not start, the most likely cause is a fault lock-out due to the following states:

• 1) Undervoltage in the vehicle network
  
• 2) Overheating of the independent heating
  
• 3) Fuel lack
  

• Re. 1) If undervoltage is determined in the vehicle network, starting the independent / auxiliary heating unit is prevented. Check the battery condition and the alternator; if necessary, recharge the battery. Ask the customer regarding his or her driving profile. In the case of a driving profile with frequent short distance driving, tell the customer about the unfavourable charge balance of the battery. Explain the resulting restrictions in the availability of the independent heating function.
  
• Re. 2) If overheating in the independent heating is determined, the independent heating is not started. Check the coolant level and, if there is a suspicion of leaking, check the leak-tightness of the cooling circuit. If appropriate, check the composition of the coolant. Check the solenoid valves of the cooling circuit according to the instructions and check with regard to faulty switching operations. Check the coolant hoses for kinks, faulty hose clamps and general damage. To initialise a renewed successful starting operation, let the independent heating cool down and reset the lock.
  
• Re. 3) The independent / auxiliary heating unit attempts to start up to three times. If this does not succeed, the control unit is locked. The minimum necessary fuel level is 8 litres of fuel, i.e. if the fuel level is at reserve or lower, the independent heating does not work. To remedy this, ensure that the fill level in the fuel tank is adequate and then reset the fault lock-out. If there is an adequate fill level, check all hose lines for kinks and leaks.
  
• 4) Furthermore, a fault code memory entry in the IHKA control unit can prevent the independent / auxiliary heating unit from starting. This fault code memory entry (K-Bus fault) indicates a fault in the communication between the IHKA control unit and the independent / auxiliary heating unit. In this case, delete the fault code memory of the IHKA control unit and repeat the starting operation (comply with test plan).
  

Information on possible fault code memory entries in the control unit of the independent heating

• Fault in the circulation pump
  If a fault is stored for the circulation pump, check the contacts with regard to loose or broken pins as well as for corrosion. Check the lines for visible damage. There is also the possibility to activate the circulation pump manually with a voltage of 12 Volts and to check the current consumption with a multimeter. If the fault is entered again after a preceding positive check of the circulation pump, then a faulty output of the control unit can be assumed.
  If the circulation pump has been replaced, ventilate the cooling circuit according to instructions.
  
• Fault in the fuel metering pump
  If a fault is stored for the fuel metering pump, check the contacts with regard to loose or broken pins as well as for corrosion. In the event of corrosion damage that cannot be unambiguously attributed to damaged seals on the connector housing, check the insulation of the complete set of wires and identify the position of the coolant inlet. Check the earth connection as well as the control line of the fuel metering pump.
  The fuel metering pump is an electromagnetic piston-stroke pump. During operation, this pump is activated by a rectangular signal (1.3 to 2.7 Hz). As a check, the fuel metering pump can be tested by manually supplying an activation pulse. Applying a voltage of 12 Volts executes a single piston stroke that can be perceived by a clearly audible clocking sound.
  If the fault is entered once again after a preceding positive check of the fuel metering pump, a faulty output of the control unit can be assumed.
  
• Flame failure fault
  If a flame failure is detected by the control unit, check the exhaust system and the combustion air intake. In doing so, pay particular attention to (partial) closures in the exhaust system and kinks. Also check the distance between the fuel extraction pipe and the base of the surge chamber. The fuel level in the surge chamber may only drop insignificantly after switching off the engine. Another possible cause for a flame failure can be faulty tank ventilation. Check the fuel supply (ensure bubble-free supply) and pay attention to faulty hose clamps, leak and kinks. Check the delivery volume of the fuel metering pump in line with instructions.
  If air has been taken in by the fuel metering pump due to the fuel level being too low, error-free operation of the independent / auxiliary heating unit is possible once again after the second start at the earliest (line completely filled). Furthermore, a longer period in which the independent / auxiliary heating unit is not used can lead to the fuel in the line evaporating.
  

Observe the following parameters for diagnosis of the independent heating:

Unlocking the independent / auxiliary heating unit

• The independent / auxiliary heating unit can be reset using the service function Unlock independent / auxiliary heating unit.
  
• A manual reset is also possible. To do so, perform the following steps:
  
  • Switch on the independent / auxiliary heating unit using the switch
    
  • Within 60 seconds, interrupt the power supply (terminal 30) by removing the fuse. Then leave the power supply interrupted for at least 2 seconds.
    
  • Switch off the independent / auxiliary heating unit. Reinsert the fuse.
    

No liability can be accepted for printing or other errors. Subject to changes of a technical nature