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Detaching and attaching auxiliary heater add-on components > < Operation of heater coolant shut-off valve N279

A5

Removing and installing heater coolant shut-off valveN279
Removing and installing heater coolant shut-off valve -N279-
  Note
t  In the event of problems with poor heating of the passenger compartment in auxiliary heating mode and poor heating of the passenger compartment with the engine running, check incorporation of the heater coolant shut-off valve -N279- into the coolant circuit and actuation of the heater coolant shut-off valve -N279- by the supplementary heater control unit -J364- → Chapter and → Vehicle diagnostic, testing and information systemVAS 5051/, “Guided fault-finding function”.
t  Different versions of -N279- (for Audi A5 Coupé, Audi A4 and Audi Q5); pay attention to correct assignment → Electronic parts catalogue.
Special tools and workshop equipment required
   
t  Hose clamps up to Ø 25 mm -3094-
  W00-0079
t  Hose clip pliers -VAS 6340- (or pliers for spring strap clips -VAS 5024/-)
Removing
–  Switch off ignition (and auxiliary heater).
  W00-1179
–  Detach the rubber seal -B- on the left to the necessary extent → General body repairs, exterior; Rep. Gr.50.
–  Remove the cover for the fresh air intake at the scuttle panel trim -A- or the scuttle panel trim (different versions) → General body repairs, exterior; Rep. Gr.50.
  Note
t  If necessary, carefully detach the scuttle panel trim from the fastener at the cross-member of the windscreen -C- → General body repairs, exterior; Rep. Gr.50.
  A87-10422
t  The method of attaching the heater coolant shut-off valve -N279--B- in the plenum chamber depends on the vehicle. On the Audi Q5, -N279- is mounted for example at a bracket -A- (which is attached to the bottom of the plenum chamber). In addition, the bracket is held in position by way of the support -C- at the plenum chamber bulkhead. The bracket -A- and the support -C- are not bolted directly to the body. To reduce the noise level, use is made of a rubber grommet for attachment with the studs and nuts -D-.
t  The following illustration shows the arrangement of the heater coolant shut-off valve -N279- on an Audi A5 Coupé. On the Audi A4 and Audi Q5 the arrangement of the heater coolant shut-off valve -N279- is slightly different. On these other vehicles the work is however to be performed in the same manner as described for the Audi A5 Coupé.
t  There are different versions of -N279- (with 3 or 4 connections for coolant hoses). On the version with 4 connections, one connection is sealed with a cap.
t  Depending on the model and the engine, the vehicle may additionally be fitted with a non-return valve in the coolant circuit. A certain amount of coolant then flows back to the engine via this non-return valve in the small circuit if the heater coolant shut-off valve -N279- is being actuated → Chapter.
–  Mark the arrangement of the coolant hoses at the heater coolant shut-off valve -N279-.
–  Pinch off the coolant hoses in the area of the heater coolant shut-off valve -N279- (e.g. with hose clamps up to Ø 25 mm -3094-).
  A82-10162
–  Unfasten the clamps -A- and detach the coolant hoses.
–  Unplug the connector -C-.
–  Screw out the bolts -B- from the heater coolant shut-off valve -N279-.
–  Remove the heater coolant shut-off valve -N279-.
Installing
Install in reverse order; paying attention to the following:
–  Butt-joint the coolant hoses.
–  Bleed the coolant circuit → Chapter.
–  If applicable, check actuation and operation of the heater coolant shut-off valve -N279- → Vehicle diagnostic, testing and information systemVAS 5051/, “Guided fault-finding function”.
Tightening torques → Chapter
  A82-10114

Detaching and attaching auxiliary heater add-on components > < Operation of heater coolant shut-off valve N279