Checking activation of supplementary heater — AUDI

Checking activation of supplementary heater
Components involved in activation of supplementary heater:
Heat energy is added to the air after it leaves the heat exchanger for the heater
1
via the
auxiliary air heater element
Z35
2
Vehicle diagnostic tester
(
“Guided Fault Finding”
). However, one condition is that the
engine control unit
J623
receives a request from the
Climatronic control unit
J255
.
Note
To protect the
battery
A
on vehicles with a start/stop system, the activation of the auxiliary air heater element
Z35
is switched off while the stop function is active. If a request has been received,
Z35
is activated again as soon as the engine has been re-started via the start function
Vehicle diagnostic tester
(
“Guided Fault Finding”
).
Cut-in criteria for activation of supplementary heater
The cut-in conditions must be fulfilled in the
J255
and
engine control unit
J623
.
The following conditions must be met for the
J255
to transmit a request for activation of the supplementary heater to the
engine control unit
J623
:
The
“Automatic supplementary heating”
function is not deactivated (indicated on the central display of the dash panel insert
2
, adjusted via the
multimedia system operating unit
E380
1
)
Owner's Manual
.
Engine running for at least 8 seconds and engine speed higher than 500 rpm.
Engine temperature below 75 °C
Calculated ambient temperature below 6 ℃
Stop function of start/stop system not active.
Electrical system voltage above 12.2 V and
onboard supply control unit
J519
not transmitting any request preventing activation
The
J255
1
does not store faults that prevent the
Z35
from switching on.
No faults stored in
engine control unit
J623
and load of
alternator
C
is less than 30 ... 77 % (depending on version of engine control unit)
Vehicle diagnostic tester
(
“Guided Fault Finding”
).
Due to the settings on
Operating and display unit 2 for air conditioning system
E775
3
,
Operating and display unit 3 for air conditioning system
E776
4
and the temperatures measured, the
J255
has calculated the additional heat output required to reach the desired passenger compartment temperature.
More than 90 % of the air (position of temperature flaps) being routed through the heating system heat exchanger for the left or right side.
Note
The
engine control unit
J623
activates the
auxiliary air heater element
Z35
via the
low heat output relay
J359
and the
high heat output relay
J360
so that the load of the
alternator
C
does not exceed 95 %. The next stage is only switched on if the load of the alternator is below 30 ... 77 %, depending on the engine speed
Vehicle diagnostic tester
(
“Guided Fault Finding”
) and
Current flow diagrams, Electrical fault finding and Fitting locations
.
Shut-off criteria for activation of supplementary heater
Note
Activation is switched off as soon as the
“Automatic supplementary heating”
function is deactivated (indicated on the central display of the dash panel insert
2
), a cut-in criterion in the
J255
or
engine control unit
J623
is no longer met or one of the shut-off criteria is detected.
The
J255
cancels the request for activation of the electric supplementary heater under the following conditions:
One of the cut-in criteria is no longer being satisfied.
The calculated ambient temperature is greater than approx. 8 °C.
The load of the alternator
C
is above 95 %.
Less than 60 % of the air is being routed through the heating system heat exchanger for the left and right side (position of temperature flaps).
Stop function of start/stop system active.