Incorporation of auxiliary heater on vehicles with heater coolant shut-off valve N279 — AUDI

Incorporation of auxiliary heater on vehicles with
heater coolant shut-off valve
N279
Direction of coolant flow
⇒
With engine running (also in auxiliary heating mode)
⇒
In auxiliary heating mode and with
heater coolant shut-off valve
N279
not activated (e.g. when engine is running in
“Read measured value block”
function
Guided Fault Finding function of vehicle diagnostic, testing and information system VAS 5051
and
Chapter
)
→ In auxiliary heating mode and with
heater coolant shut-off valve
N279
activated (e.g. when engine is not running in
“Read measured value block”
function
Guided Fault Finding function of vehicle diagnostic, testing and information system VAS 5051
and
Chapter
)
1
Auxiliary heater
2
Circulation pump
V55
Circulation pump is activated by
auxiliary heater control unit
J364
Under certain conditions, the circulation pump may also be activated when the engine is running to assist the coolant pump of the engine (
“Read measured value block”
)
Guided Fault Finding function of vehicle diagnostic, testing and information system VAS 5051
.
Checking
Guided Fault Finding function of vehicle diagnostic, testing and information system VAS 5051
Removing and installing
Chapter
3
Heater coolant shut-off valve
N279
Removing and installing
Chapter
Incorporation into coolant circuit
Engine, mechanics; Rep. Gr. 19; Cooling system
Shut-off valve is activated by
auxiliary heater control unit
J364
Guided Fault Finding function of vehicle diagnostic, testing and information system VAS 5051
.
Currently
heater coolant shut-off valve
N279
is only activated when auxiliary heating mode is switched on and engine is not running
Illustration shows
heater coolant shut-off valve
N279
in non-activated state (coolant flow from connection
“1”
to connection
“2”
)
Chapter
.
When
heater coolant shut-off valve
N279
is activated, coolant flows from connection
“1”
to connection
“3”
Chapter
.
Depending on the engine version, the coolant hose to connection
“3”
(of the
heater coolant shut-off valve
N279
Chapter
) may be fitted with a non-return valve (not always visible from outside
Chapter
and
Electronic parts catalogue
). This stops coolant flowing against the normal direction into the heat exchanger.
4
Heat exchanger of air conditioning unit
5
Non-return valve
Not fitted with all engine versions
Engine, mechanics; Rep. Gr. 19; Cooling system
Not visible from outside, fitted in coolant hose (bleeder hose)
Chapter
and
Electronic parts catalogue
Non-return valve remains closed in auxiliary heating mode (pressure generated by circulation pump is not sufficient to open valve).
With engine running, coolant circuit is bled by way of this non-return valve.
6
Forced ventilation of coolant circuit
Incorporation into engine coolant circuit
Engine, mechanics; Rep. Gr. 19; Cooling system
7
Non-return valve
Not fitted with all engine versions
Engine, mechanics; Rep. Gr. 19; Cooling system
Not always visible from outside, may be fitted in coolant hose
Chapter
and
Electronic parts catalogue
Non-return valve remains closed in auxiliary heating mode.
This non-return valve stops coolant heated in or after auxiliary heating mode entering the engine.
Note
Under certain unfavourable conditions, there may be problems starting the engine if hot coolant ingresses into area near
coolant temperature sender
G62
at low ambient temperatures and when the engine is cold (engine control unit detects warm engine, which leads to not enough fuel being injected when engine is started).
8
Coolant supply from engine
Incorporation into engine coolant circuit
Engine, mechanics; Rep. Gr. 19; Cooling system
9
Coolant return to engine
Incorporation into engine coolant circuit
Engine, mechanics; Rep. Gr. 19; Cooling system