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Checking actuation of heating element for additional heater Z35 > < Checking the electric additional heater with a capacity of 1500 watts

A2

Checking the current consumption of the additional heater
Checking the current consumption of the additional heater
t  You can check actuation of the heating element for additional heater -Z35- in the measured value block for the engine control unit by selecting the designated display group for this function (depending on the engine control unit, e.g. display group “016”) → Relevant Workshop Manual, Diesel Direct Injection and Glow Plug System
t  The specified test requirements must be fulfilled → Chapter
–  Switch off the ignition.
–  Remove the trim from the bottom of the right pillar “A”. → General Body Assembly, Interior; Repair group 70
–  Set the measurement device used for this measurement (e.g. the Multimeter -V.A.G 1715/-) to current measurement with the use of the current probe (a current of up to a maximum of 130 A is measured).
   
–  Place the current probe from an ammeter over the earth lead -A- running to the heating element for additional heater -Z35-
–  Read the ammeter value
Specification: 0 A
–  Spray the ambient temperature sensor -G17- (installed in the area of the front bumper → Chapter) at an ambient temperature above 5 °C continuously with a cold spray until it drops below -10 °C.
–  Switch on the ignition.
–  Read the ambient temperature display in the dash panel insert; it must show a temperature below 0 °C (if necessary, spray the temperature sensor again).
  Note
t  In the case of vehicles without an ambient temperature display in the dash panel insert, you can view the ambient temperature sensor -G17- reading in measured value block “008” in the Climatronic unit → Chapter.
t  Refer to the measured value block on the engine control unit to see which cut-in conditions are met for the additional heater. → Relevant Workshop Manual, Diesel Direct Injection and Glow Plug System
–  Read the ammeter value
Specification: 0 A
–  Set the maximum heat output on the heater control or the operating and display unit for air conditioner/Climatronic -E87- (with the Econ button not pressed, the rotary knob for temperature preselection set fully to “heat” or temperature preselection “Hi”).
–  Start the engine.
–  Increase the engine speed to approx. 2000 rpm.
–  Monitor the display on the meter
After some time, the current flowing via the additional heater rises from 0 A to over 60 A.
–  Let the engine run at idling speed
–  Change the alternator load, e.g. by switching electrical consumers (heated rear window, light, etc.) on and off
–  The current flowing via the heating element for additional heater -Z35- (or the alternator load) changes.
  Note
t  You can check actuation of the heating element for additional heater -Z35- and the alternator load in the measured value block for the engine control unit by selecting the designated display group for this function (depending on the engine control unit, e.g. display group “016”) → Relevant Workshop Manual, Diesel Direct Injection and Glow Plug System
t  To ensure that the temperature of the ambient temperature sensor -G17- remains under +5 °C throughout the test, spray the ambient temperature sensor -G17- with cold spray repeatedly.
t  If there is too little current flowing (and the alternator load is under 50%, for example), even though the additional heater is actuated, check actuation of the heating element for additional heater -Z35- → Chapter.
t  Current may only flow via the heating element for additional heater -Z35- if this is actuated by the engine control unit
  A80-0221
t  As small currents cannot be measured with the current probe, if the vehicle's no-load current consumption is too great, with the ignition switched off, loosen the hexagon nut -B- at the earth point and measure the current directly via the meter; no current may flow (less than 1 mA).
  A80-0221

Checking actuation of heating element for additional heater Z35 > < Checking the electric additional heater with a capacity of 1500 watts