Operation of and removing/installing heater coolant shutoff valve N279 — AUDI

Operation of and removing/installing
heater coolant shutoff valve
N279
Function
Note
Currently only fitted to vehicles with
“Auxiliary heater”
optional extra.
Not fitted on vehicles with diesel engine on which the auxiliary/supplementary heater is only used as supplementary heater (vehicles without
“Auxiliary heater”
optional extra).
If voltage is not applied to
heater coolant shutoff valve
N279
(large coolant circuit), coolant can flow from connection
C
(from pump/valve unit) to connection
D
(to engine). Coolant (from engine) flows via connection
A
to connection
B
and from there to auxiliary/additional heater.
If voltage is applied to
heater coolant shutoff valve
N279
(small coolant circuit), coolant can flow from connection for hose
C
(from pump/valve unit) to connection
B
(to auxiliary/additional heater).
There is no flow-regulating component fitted between connections
A
and
B
.
With certain engine versions, connection
A
is sealed by means of a cap (e.g. in vehicles with 12-cyl. engine). In these vehicles, coolant from engine flows to auxiliary/additional heater via a T-piece installed between connection
B
and auxiliary/additional heater.
In auxiliary heater mode,
heater coolant shutoff valve
N279
is actuated by
additional heater control unit
J364
until coolant temperature in auxiliary heater has reached a specified value
Chapter
.
The display in the measured value block for actuation of the
heater coolant shut-off valve
N279
differs and depends on the vehicle model and the version of the
supplementary heater control unit
J364
. On the Audi A8 at present for example, a display of 100 % indicates that 100 % of the coolant is being conveyed in the large circuit and that the
heater coolant shut-off valve
N279
is not being actuated
Vehicle diagnostic, testing and information system
VAS 5051 A
, "Guided fault-finding" function.
Removing
Special tools, testers and auxiliary equipment required
Hose clamps up to Ø 40 mm
3093
or
hose clamps up to Ø 25 mm
3094
Note
On removal, note down bolt lengths and assignment for re-installation.
All cable ties and other wiring harness fasteners released or cut open on removing shutoff valve must be re-attached in same position on installation.
Switch off ignition.
Dissipate pressure in coolant circuit by opening cap at coolant expansion tank.
Engine, mechanics
Rep. Gr.
19
If the vehicle is fitted with an air cleaner above the auxiliary/supplementary heater, remove the cleaner together with the air cleaner housing
Injection and ignition system
Rep. Gr.
24
and
Injection and glow plug system
Rep. Gr.
23
.
Remove noise insulation and front right wheel housing liner
General body repairs, Exterior
Rep. Gr.
50
Remove right headlight.
Electrical system
Rep. Gr.
94
Move the lock carrier to service position
General body repairs, Exterior
Rep. Gr.
50
Pinch off the coolant hoses
A
,
B
and
C
(to the
heater coolant shut-off valve
N279
) and
D
(to the auxiliary/supplementary heater).
Detach coolant hoses
B
and
C
from
heater coolant shutoff valve
N279
.
Detach coolant hoses
A
and
C
from
heater coolant shutoff valve
N279
.
Unplug connector
C
.
Remove hexagon nuts
D
.
Remove
heater coolant shutoff valve
N279
E
.
Installing
Re-install components removed in reverse order.
Bleed the coolant circuit
Chapter
and
Engine, mechanics
Rep. Gr.
19
.
If applicable, check actuation and operation of the
heater coolant shut-off valve
N279
"Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.