Auxiliary Heater, Checking (AUDI A6 E-Tron)

• The High-Voltage Heater (PTC) -Z115- -1- has a normal output of approximately 5000 W (Watt). The nominal output is only yielded when the circulating coolant has a low temperature (for example at a coolant inlet temperature of -20 °C (-4 °F) and a coolant flow of 8 l/ min.).

  Courtesy of AUDI OF AMERICA, LLC

• The output released to the circulating coolant depends strongly on the temperature and amount of the coolant which flows through the High-Voltage Heater (PTC) -Z115-. If the flow rate is too low, the coolant in the High-Voltage Heater (PTC) -Z115- warms up to a greater extent. The delivered energy amount, however, is reduced due to the missing amount.
• The High-Voltage Heater (PTC) -Z115- is not designed for any specific flow direction. A clean ventilation of the High-Voltage Heater (PTC) -Z115- is however dependent on the installation position of a specific coolant circulation flow -arrows-. Therefore the coolant hoses must be connected on the correct side (the upper coolant hose toward the heater core in the A/C unit). Refer to COMPONENT LOCATION OVERVIEW - ENGINE COOLANT CIRCUIT .

The components involved with the activation of the auxiliary heater:

• Heat energy is supplied to the coolant before entering the heater core for the heater (in the A/C unit) via the High-Voltage Heater (PTC) -Z115- -1-. Refer to COMPONENT LOCATION OVERVIEW - ENGINE COOLANT CIRCUIT and use the Vehicle Diagnostic Tester in the "Guided Fault Finding"  function. Required for this is, for example, that there is a request from the Climatronic Control Module -J255- control head to the Thermal Management Control Module -J1024-.
• If the Thermal Management Control Module -J1024- determines that heating output is necessary, the Thermal Management Control Module -J1024- checks various control modules through the data bus (for example, the Battery Regulation Control Module -J840-, installed in the Hybrid Battery Unit -AX1-, the High-Voltage Battery Charger Control Module -J1050-, etc.). If no conditions are determined by these control modules, which prohibit the activation of the High-Voltage Heater (PTC) -Z115-, then the Thermal Management Control Module -J1024- activates the High-Voltage Heater (PTC) -Z115- (through the High-Voltage Heater (PTC) Control Module -J848-). For additional information. Refer to PARKING AIR CONDITIONER (ONLY ON VEHICLES WITH HIGH-VOLTAGE SYSTEM) , the appropriate WIRING DIAGRAM and use the Vehicle Diagnostic Tester in the "Guided Fault Finding"  function.
• In order for the coolant warmed by the High-Voltage Heater (PTC) -Z115- to be supplied through the A/C unit heater core for the heater with the engine running, in electric drive mode (with the engine off) and with the "parking air conditioner" function active (ignition is switched off), the Thermal Management Coolant Pump 2 -V618- and the Coolant Change-Over Valve 3 -N634- must also be activated and their function must be OK. For more information, refer to PARKING AIR CONDITIONER (ONLY ON VEHICLES WITH HIGH-VOLTAGE SYSTEM)  a (Connection Diagram for Coolant Hoses). Use the Vehicle Diagnostic Tester in the "Guided Fault Finding"  function) and to the appropriate WIRING DIAGRAM.
• On vehicles with a high-voltage system (Audi A6 e-tron) and a parking heater installed as optional equipment, the parking heater is activated as the auxiliary heater or the High-Voltage Heater (PTC) -Z115- is activated by the Thermal Management Control Module -J1024- under certain circumstances. For additional information, refer to PARKING AIR CONDITIONER (ONLY ON VEHICLES WITH HIGH-VOLTAGE SYSTEM)  (Information on Operating Parking Heater on Vehicles with High-Voltage System).
• The Climatronic Control Module -J255- control head, the Thermal Management Control Module -J1024- and the High-Voltage Heater (PTC) Control Module -J848- installed in the High-Voltage Heater (PTC) -Z115- exchange data with each other through the data wires to switch the High-Voltage Heater (PTC) -Z115- on and off. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding"  function and refer to the appropriate WIRING DIAGRAM.

Criteria to activating the High-Voltage Heater (PTC) -Z115-. 

• The Climatronic Control Module -J255- control head sends a request to the Thermal Management Control Module -J1024- to switch on the auxiliary heater. The Thermal Management Control Module -J1024- prompts various control modules through the data bus. When the requirements stored in the Thermal Management Control Module -J1024- are met and no fault is detected by the High-Voltage Heater (PTC) Control Module -J848-, the High-Voltage Heater (PTC) -Z115- is activated by the High-Voltage Heater (PTC) Control Module -J848-. If a requirement in the Thermal Management Control Module -J1024- to activate the High-Voltage Heater (PTC) -Z115- is not met, no request will be sent or the activation is switched off.
• The operating conditions must be met in the Thermal Management Control Module -J1024- or there will not be any activated shut-off condition. A list of switch-on criteria can be found in the Vehicle Diagnostic Tester in the "Guided Fault Finding"  function (for the Thermal Management Control Module -J1024-).

Switch-Off Criteria for Auxiliary Heater Activation

The Thermal Management Control Module -J1024- switches off the prompt to switch on the High-Voltage Heater (PTC) -Z115-, if a switch-on requirement is no longer met or the High-Voltage Heater (PTC) Control Module -J848- detects a fault.