Checking activation of electric supplementary air heater — AUDI

Checking activation of electric supplementary air heater
Fitted on vehicles with TDI engine and vehicles with high-voltage system (hybrid vehicles with petrol engine)
Note
Vehicles with a TDI engine and no auxiliary heater and vehicles with a high-voltage system (hybrid vehicles with petrol engine) are fitted with an electric supplementary air heater
Audi sales literature
.
Vehicles with TDI engine and
“auxiliary heater”
as optional equipment are currently not fitted with an electrical
auxiliary air heater element
Z35
for supplementary heating. There, the auxiliary heater performs the task of the auxiliary air heater
Auxiliary/supplementary heater
Rep. gr.
82
Coolant circuit with auxiliary/supplementary heater; Connection diagram - coolant hoses
Except for vehicles with high-voltage system, vehicles with petrol engine are currently not fitted with a supplementary heater (an
“auxiliary heater”
fitted as optional equipment is not activated as a supplementary heater).
Vehicles with a high-voltage system (hybrid vehicles) and petrol engine are currently equipped with an electrical
auxiliary air heater element
Z35
to provide a supplementary heating function
Chapter
.
On vehicles with a petrol engine, the electric supplementary heating (
auxiliary air heater element
Z35
) is activated by a signal from the operating unit (
Climatronic control unit
J255
) by way of the local data bus (via the same output by which the
fresh air blower control unit
J126
is activated) to the
auxiliary air heater control unit
J604
. In the event of problems with the
fresh air blower control unit
J126
or the
fresh air blower
V2
on these vehicles, also check the
auxiliary air heater control unit
J604
Vehicle diagnostic tester
in
“Guided Fault Finding”
mode and
Current flow diagrams, Electrical fault finding and Fitting locations
.
Make sure you have the correct version of
J126
; on vehicles with high-voltage system (hybrid vehicles) and petrol engine, for instance, additional information is transmitted via the local data bus to activate
J604
Electronic parts catalogue
.
On vehicles with a start/stop system, the
auxiliary air heater element
Z35
is deactivated while the stop function is active (to protect the battery).
The
auxiliary air heater element
Z35
is activated again via the engine control unit after the engine has been re-started by the automatic start function
Vehicle diagnostic tester
in
“Guided Fault Finding”
mode.
Heat energy is supplied to the air after leaving the heat exchanger in the event of a request from the operating unit,
Climatronic control unit
J255
.
The
auxiliary air heater element
Z35
is activated by the
low heat output relay
J359
and the
high heat output relay
J360
by way of the corresponding engine control unit (or the
auxiliary air heater control unit
J604
on vehicles with petrol engine) when a request is transmitted by the operating unit (
Climatronic control unit
J255
). The corresponding information is exchanged between the operating unit (
Climatronic control unit
J255
) and the engine control unit /
J604
via the data bus
Vehicle diagnostic tester
in
“Guided Fault Finding”
mode and
Current flow diagrams, Electrical fault finding and Fitting locations
.
Checking actuation of electric supplementary air heater operation is described in the
Vehicle diagnostic tester
in
“Guided Fault Finding”
mode for the air conditioner on
J255
.
The function
“Read measured values”
for the air conditioner on
J255
indicates that the request for activation of the supplementary heater (electric supplementary heater or auxiliary heater as supplementary heater) is being transmitted to the engine control unit /
J604
Vehicle diagnostic tester
in
“Guided Fault Finding”
mode .