Checking heating output — AUDI

Checking heating output
Note
This Workshop Manual only gives a general outline of the checking procedure. Perform the functional check of the heater as described in the "Guided Fault Finding" routine
Vehicle diagnostic tester
(
“Guided Fault Finding”
).
Special tools and workshop equipment required
Vehicle diagnostic tester
Commercially available thermometer (for measuring temperature; if applicable use thermometer with 2 probes for simultaneous measurement of temperature e.g. on right and left)
If the coolant circuit is not completely bled after filling, air may accumulate in the heat exchanger and thus reduce the heating output. In addition, there may be problems with noises or with differences in the temperature of the air from the vents.
Remedy if there is poor heating output or noise from the coolant circuit
Perform a road test at a fairly high engine speed (for at least 10 minutes, engine speed above 2500 rpm). Select a low gear when doing so to avoid excessive road speeds.
If a customer complains about poor heating output at certain engine speeds, check the connections between the heat exchanger and the engine coolant circuit
Rep. gr.
19
Cooling system/coolant; Connection diagram - coolant hoses
.
Note
On vehicles with start/stop function and a manually controlled air conditioner (with heater and without air conditioner), the stop function may be disabled depending on the setting on the operating unit (
air conditioning system control unit
J301
/
heater control unit
J65
), e.g. in heating mode. The engine is started as soon as there is a request for heating. In cooling mode, there are no limitations for the stop function via
J301
(
J65
).
On vehicles with a start/stop system and an automatically controlled air conditioner, the stop function is disabled depending on the setting on the operating unit (
Climatronic control unit
J255
). For example, the stop function is not possible, or the stop function is interrupted and the engine is switched on as soon as the
“defrost”
mode is selected. This also applies if the difference between the set specified temperature and the measured actual temperature exceeds a certain value in heating and cooling mode
Vehicle diagnostic tester
.
On vehicles with start/stop system, no additional coolant pump is currently installed for the start/stop function. However, depending on the vehicle's engine, an electric coolant pump (activated by the engine control unit) may be installed
Rep. gr.
19
Coolant pump/thermostat assembly; Exploded view - electric coolant pump
and
Current flow diagrams, Electrical fault finding and Fitting locations
.
Depending on the engine version, a
continued coolant circulation pump
V51
/
auxiliary pump for heating
V488
(different designations depending on engine version) may be fitted to assist the engine coolant pump
Engine, mechanics
Rep. gr.
19
Cooling system/coolant; Connection diagram - coolant hoses
and
Current flow diagrams, Electrical fault finding and Fitting locations
. On vehicles with a start/stop system,
V51
/
V488
may be activated in
“stop mode”
(engine stopped), e.g. if the engine is cold, to maintain the flow of coolant through the heat exchanger.