Removing and installing left heat regulation valve N175 and right heat regulation valve N176 — AUDI

Removing and installing
left heat regulation valve
N175
and
right heat regulation valve
N176
WARNING
Risk of burns.
Even if the engine is cold, the heat regulation valve unit may be warm or even hot as, with the ignition on, it is constantly actuated as a function of the temperature setting at the operating unit,
Climatronic control unit
J255
.
Note
The heat regulation valve unit is open when deenergized. If the power supply or the valve connection to the operating unit,
Climatronic control unit
J255
is interrupted, the air conditioner heat output cannot be regulated (the air conditioner provides constant heating)
Current flow diagrams, Electrical fault finding and Fitting locations
.
In the event of a problem with
“poor heat output”
, check the following before removing the heat regulation valves:
Connection of heat regulation valves and air conditioning unit heat exchanger return to engine coolant circuit (proper assignment of supply and return connection to engine); interchanging the two connections would cause the engine coolant pump to work in opposition to the
coolant circulation pump
V50
Possible interchange of wiring to
coolant circulation pump
V50
(
“+”
and
“-”
); interchanging the connections would cause the pump to run in the wrong direction (and work in opposition to the engine coolant pump)
Current flow diagrams, Electrical fault finding and Fitting locations
Bleeding of coolant circuit; bleed again if necessary
Rep. gr.
19
Heat output of air conditioner
Chapter
Special tools and workshop equipment required
Hose clamps up to 25 mm
3094
(3x)
Removing
Switch off the ignition.
WARNING
Danger of scalding from hot vapour and hot coolant
The cooling system is pressurised when the engine is warm.
To dissipate the pressure, cover the coolant expansion tank cap with a cloth and open carefully.
Open the coolant expansion tank cap.
Remove the cover for the transmission tunnel
1
.
Remove the propshaft
Rear final drive
Rep. gr.
39
.
WARNING
Risk of burns.
Even if the engine is cold, the heat regulation valve unit may be warm or even hot as, with the ignition on, it is constantly actuated as a function of the temperature setting at the operating unit,
Climatronic control unit
J255
.
Mark the arrangement of the coolant hoses
F
(supply to left heat exchanger) and
B
(supply to right heat exchanger) for re-installation.
Pinch off the coolant hoses
A, B, F
with hose clamps
3094
.
Detach the pipe holder
C
from the stud.
Unscrew the nut below it.
Tightening torque 8 Nm
Unplug the connector
D
.
Detach the coolant hoses
A, B and F
from the heat regulation valve unit
E
.
Detach the heat regulation valve unit.
Installing
Install in reverse order, paying attention to the following:
Note
The
coolant circulation pump
V50
is not to be started up until the coolant circuit has been bled (dry running would destroy the
coolant circulation pump
V50
).
The two heat regulation valves
N175
and
N176
must be open for bleeding the coolant circuit (they are open when not actuated).
Unplug the connectors at the heat regulation valve unit and the
coolant circulation pump
V50
.
Bleed the coolant circuit
Rep. gr.
19
.
Plug the connectors back in at the
coolant circulation pump
V50
and the heat regulation valve unit.
Note
Coolant circulation pump
V50
and heat regulation valve
N175
/
N176
faults are detected by the operating unit,
Climatronic control unit
J255
and stored if the ignition is switched on with the connector unplugged.
Install the propshaft
Rear final drive
Rep. gr.
39
.
Fit the cover for the transmission tunnel
Rep. gr.
66
.
On completion of repair work, perform the following operations on the operating unit,
Climatronic control unit
J255
Vehicle diagnostic, testing and information system
VAS 5051/
, "Guided fault-finding" function
:
Interrogate the event recorder and erase any faults displayed.
Implement final control diagnosis.