Recirculated Air Mode; Temperature Control - Volvo 850 Supplement Manual

RECIRCULATED AIR MODE

The ECC control module selects recirculated air mode only for
a combination of cooling and high outside temperature, provided that:
* There is a considerable difference between the desired and
actual temperature on driver's side. The quantity of
recirculated air will vary between 70-100 percent, depending
on difference in temperature.
* A high fan speed is manually selected. In this case, the
recirculation damper will be set to a mid-position (50
percent of the air will be recirculated).
Recirculation Motor
This motor operates the recirculation damper by means of a
mechanical linkage in response to signals from ECC control module.
Recirculation Switch
The off position of REC (recirculation) switch corresponds to
automatic operation, the ECC control module determines whether
recirculation is required.
Air Distribution Switch
With air distribution switch in defroster position,
recirculated air mode always cuts out, as humidity in passenger
compartment will normally be higher than that of outside air.
Recirculation Damper
In AUT (automatic) mode, recirculation damper movement is
limited to fractions of a second. It takes about half a minute from
full recirculation to take effect if outside temperature is high.

TEMPERATURE CONTROL

Individual temperature control is provided by the driver's
and passenger's side temperature control damper motors in response to
signals from ECC control module.
The ECC control module computes temperature control damper
motors based on inputs from temperature dial settings, duct
temperature sensors, interior temperature sensors, solar sensor,
engine coolant temperature sensor, and outside (ambient) temperature
sensor.
The air temperature is monitored downstream of temperature
control dampers by the duct temperature sensors. The difference
between the desired and actual interior temperature, as monitored by
interior temperature sensors, has a direct effect on temperature
control damper positions.
In direct sunlight, the temperature control dampers are
positioned to provide a lower temperature, as determined by solar
sensor input. If the engine is cold and outside temperature is low,
the temperature control dampers are set for more heat to reach the
desired temperature faster.
TROUBLE SHOOTING
SELF-DIAGNOSTICS
The Electronic Climate Control (ECC) control module can
detect faults in the system and store Diagnostic Trouble Codes (DTCs).
If a fault is present, system informs driver by flashing AC OFF and
REC switch LEDs for 20 seconds.
A fault warning is given when a fault is discovered or