Audi Workshop Service and Repair Manuals

Notes:

• ◆ Vehicles with diesel engine are currently fitted with an electric additional heater (heat energy is added to air flow after exiting from heat exchanger).

=> Audi Sales Range

• ◆ Vehicles with diesel engine and "auxiliary heater" as optional extra may not be fitted with an electric additional heater depending on vehicle control system. On such vehicles, this function is assumed by the auxiliary heater, which operates as a fuel-driven additional heater (by adding additional heat energy to the coolant).

=> Audi Sales Range

=> Auxiliary heater

• ◆ Vehicles with petrol engines are not currently equipped with an additional heater.
• ◆ Checking actuation of heating elements

=> Relevant Diesel Direct-injection and Glow Plug System Workshop Manual; Repair Group 01

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

• ◆ On vehicles with electric additional heater, operating and display unit for air conditioner/Climatronic -E87 (heating) actuates engine control unit via bus system (control unit with display in dash panel insert -J285 is interface between convenience and drive train data buses). Control unit then decides whether to switch on additional heater. Depending on engine control unit version, display appears in various engine control unit measured value blocks to indicate why additional heater has not been switched on or that it has been actuated.

=> Relevant Diesel Direct-injection and Glow Plug System Workshop Manual; Repair Group 01

• ‒ -E87 (heating) transmits request for cut-in of electric additional heater via bus system to engine control unit (and to additional heater control unit -J364) if:
• ‒ -E87 (heating) is encoded for diesel engine (depending on -E87 version, not mandatory)
• ‒ Ambient temperature determined is less than 5 °C or has been at least once since ignition was switched on
• ‒ Engine is running
• ‒ Specified vent temperature calculated by -E87 (heating) was greater than 45 °C and is still more than 40 °C

• ‒ Coolant temperature transmitted by dash panel insert and calculated by -E87 (heating) is less than 70 °C (under certain conditions less than 80 °C)

• ◆ Electric additional heater is only switched in by diesel direct-injection and glow-plug system control unit if certain conditions occur simultaneously.

=> Relevant Diesel Direct-injection and Glow Plug System Workshop Manual; Repair Group 01

• ‒ Engine control unit switches on additional heater if the following prerequisites are met:
• ‒ Operating and display unit for air conditioner/Climatronic -E87 (heating) transmits request via data bus system
• ‒ Engine speed greater than 600 rpm
• ‒ Coolant temperature less than 70 °C (less than 80 °C at very low ambient temperatures)
• ‒ Capacity utilisation of alternator -C less than 60% (only with electric additional heater)

=> Relevant Diesel Direct-injection and Glow Plug System Workshop Manual; Repair Group 01

Checking

• ‒ Remove driver's storage compartment to measure additional heater elements.

=> General Body Repairs, Interior; Repair Group 68

• ‒ → Unplug connectors -A- , -B- and -C- from heating element.
• ‒ Check individual heating elements. Measured value between the individual contacts (from contact D1 to contact F2) is a function of temperature and is between 0.2 and 5 ω.

Notes:

• ◆ The additional heating heater element -Z35 consists of several layers of resistor elements with a joint heating capacity of 1000 W (actuation of all 3 inputs). These resistor elements have a positive temperature coefficient (resistance increases with temperature and current input decreases).

• ◆ The resistor heating elements are actuated individually. As however all are interlinked in -Z35, the current is discharged via the earth connection with the lowest resistance.
• ◆ -Z35 is designed such that - when switched on - the current flowing via any of the contacts can never exceed 35 A (immediately following switch-on, resistance increases and current decreases).
• ◆ Attainment of the maximum heat output of 1000 W (3 x 333 W) requires the temperature of the resistor heating elements to be low and an adequate supply of current by the alternator.

=> Relevant Diesel Direct-injection and Glow Plug System Workshop Manual; Repair Group 01

• ◆ As resistances of less than 10ωcannot be measured with sufficient accuracy using workshop equipment, it is not possible to determine a short circuit in the additional heater element.

• ‒ → Actuate relays for "low" and "high" heat output by way of "Final control diagnosis" function of appropriate engine control unit and in doing so measure voltage between the two contacts of connectors -A-, -B- and -C-.

=> Relevant Diesel Direct-injection and Glow Plug System Workshop Manual; Repair Group 01

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

Notes:

• ◆ → The engine control unit actuates -Z35 in 3 stages. This involves voltage being applied to the contacts in the connectors -A-, -B- and -C- as follows (consult appropriate current flow diagram for connection details).
• ‒ For stage "1", low heat output relay -J359 applies voltage to one connector
• ‒ For stage "2", stage "1" is deactivated and voltage is switched via the high heat output relay -J360 to the other two connectors
• ‒ For stage "3", stage "2" is supplemented by stage "1"

=> Relevant Diesel Direct-injection and Glow Plug System Workshop Manual; Repair Group 01

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

• ◆ Alternator capacity utilisation is constantly monitored by engine control unit. If this remains below a certain limit, the next stage is switched in, whereas exceeding a specified limit results in switching down a stage.