Auxiliary Heater Heating Element -Z35-, CHECKING: Notes
Special Tools And Workshop Equipment Required
- Vehicle Diagnostic Tester with Vehicle Diagnosis System - Trigger Clamp - 100A :VAS5051B/7
Auxiliary Heater Heating Element -Z35- with Auxiliary Heater Control Module -J604-
An electric auxiliary heater is currently installed in vehicles with diesel engine. In this system, the air is supplied with heat energy after it has left the heater core of the heater in the event a there is a request from the heater controls (the Heater Control Module -J65-). Activation of the electric auxiliary heater occurs via the engine control module (Low Heat Output Relay -J359- and the High Heat Output Relay -J360-). Refer to Vehicle Diagnostic Tester in the Guided Fault Finding function (Guided Fault Finding for the respective engine control module) and refer to the Appropriate Wiring Diagram.
Can be checked. Refer to Vehicle Diagnostic Tester under Heating, Ventilation and Air Conditioning; OBD-Capable Systems; Auxiliary Heater; Electrical Components.
A start-stop system is available as optional equipment for certain engines of this vehicle. For vehicles with a Start/Stop System, the Auxiliary Heater Heating Element -Z35- activation is switched off for the time in which the stop function is active (to protect the Battery -A-). After the engine has started with the start function, the Auxiliary Heater Heating Element -Z35- is reactivated. Refer to Vehicle Diagnostic Tester in the Guided Fault Finding function.
Test Conditions
- Exterior temperature less than 5 °C (41 °F)
- Coolant temperature less than 80 °C (176 °F)
- Vehicle interior temperature approximately 20 °C (68 °F)
- Battery voltage is greater than 11 V
- Generator load is not greater than 50 % (terminal DF)
- Engine speed higher than 450 RPM
- Turn the interior temperature control to maximum heating (select the high setting on vehicles with Climatronic).
Test Sequence
-- Remove the front footwell center console trim panel. Refer to CENTER CONSOLE .
-- Remove the driver side footwell vent. Refer to DRIVER SIDE FOOTWELL VENT, REMOVING AND INSTALLING .
-- Measure the current draw at the ground wire -arrow-. Refer to Vehicle Diagnostic Tester and the :VAS5051B/7
Low heat output ≈ 30 amp
Medium heat output ≈ 60 amp
High heat output ≈ 80 amp
Auxiliary Heater Heating Element -Z35-, Switch-On Criteria For the Activation
The engine control module actuates the Auxiliary Heater Heating Element -Z35- via the Low Heat Output Relay -J359- and High Heat Output Relay -J360- in the event the following requirements are met:
- There is a ground signal at the engine control module from the Heater Control Module -J65-.
- Engine is running for a minimum of 8 seconds and engine speed is greater than 500 RPM.
- The engine temperature is less than 75 °C (167 °F).
- The calculated exterior temperature is less than 8 °C (46 °F).
- The electrical system voltage is greater than 12.2 volts and no request that forbids the switch-on is sent by Vehicle Electrical System Control Module -J519-.
- No DTC is stored in the engine control module and the Generator -C- load is between 30 to 77 % (depending on the engine speed).
The engine control module actuates both auxiliary heater relays for the Auxiliary Heater Heating Element -Z35- so that the load on the Generator -C- does not exceed 95%. Refer to Vehicle Diagnostic Tester in the Guided Fault Finding function (for the engine control module) and refer to the Appropriate Wiring Diagram. Thus the next stage only is switched on if the Generator -C- load is between 30 to 77 %, depending on the engine speed.
Auxiliary Heater Heating Element -Z35-, Activation Switch-On Criteria
For vehicles without an A/C system, the activation is switched off as soon as one of the switch-on requirements is no longer met in engine control module or one of the switch-off criteria is detected.
- When one of the switch-on requirements is no longer met.
- The calculated exterior temperature is greater than 11 °C (52 °F).
- The Generator -C- load is greater than 95 %.
- There is no longer a ground signal at the engine control module from the Heater Control Module -J65-.