Volvo 850. Instruction - page 58
A/C-HEATER SYSTEM - AUTOMATIC
1995 Volvo 850
1995-96 Auto. A/C-Heater Systems
Volvo 850
* PLEASE READ THIS FIRST *
WARNING: To avoid injury from accidental air bag deployment, read and
carefully follow all SERVICE PRECAUTIONS and DISABLING &
ACTIVATING AIR BAG SYSTEM procedures in the AIR BAG RESTRAINT
SYSTEM article in the ACCESSORIES/SAFETY EQUIPMENT section.
CAUTION: When battery or radio is disconnected, radio will go into
anti-theft protection mode. Obtain radio code anti-theft
protection code from owner prior to servicing vehicle.
A/C SYSTEM SPECIFICATIONS
SPECIFICATIONS
Application Specification
Compressor Type .................... Zexel DKS-15CH 6-cyl.
Compressor Belt Tension (1)
Compressor Oil Capacity ..................... ( 2) 6.8 ozs.
Refrigerant Capacity (R-134a) .................. 26.4 ozs.
System Operating Pressures (3)
High Side ............... 406-450 psi (28.5-31.6 kg/cm
)
Low Side .................... 25-33 psi (1.8-2.3 kg/cm
)
(1) - Belt tension is maintained by automatic belt tensioner.
(2) - Use PAG Oil (Part No. 11 61 407-0)
(3) - Pressure switch cut-out points.
DESCRIPTION
The Electronic Climate Control (ECC) module (A/C-heater
control panel) contains a function selector dial, driver’s and
passenger’s temperature dials, a REC (recirculated air) switch, A/C
OFF switch, and a fan speed (blower motor) control lever. See Fig. 1.
The heater (blower motor) fan is controlled by ECC output (power)
stage. Air conditioning system will only operate above 32
F (0
C).
Blower switch must not be in zero position to allow compressor to
engage.
Other system components include an A/C relay, A/C compressor,
low-pressure switch (pressostat), A/C safety and high-pressure switch,
engine coolant temperature sensor, outside temperature sensor,
interior temperature sensors, and duct temperature sensors.
In addition, driver’s and passenger’s temperature control
damper motors, recirculation damper motor, floor/defroster damper
motor, ventilation damper motor, and diagnostic connectors (units)
complete system.
Fig. 1: Identifying ECC Control Panel
Courtesy of Volvo Cars of North America.
OPERATION
A/C COMPRESSOR CLUTCH CONTROL
The A/C compressor electromagnetic clutch is powered by the
A/C relay. Compressor operation requires that the A/C relay be
activated by both Electronic Climate Control (ECC) module and Engine
Control Module (ECM). The ECM turns A/C compressor off when engine is
at full acceleration, at high engine temperature, and for 5-10 seconds
after starting engine.
The ECC control module normally supplies voltage to A/C
relay, except when heater (blower motor) fan is off and vehicle speed
is less than 20 MPH, when heater fan is off and recirculation is on,
or momentarily when under full acceleration.
If A/C is switched off using the AC OFF switch, ECC control
module will cut supply voltage to relay, turning off compressor.
However, this does not apply when air distribution control is in
defrost setting, since A/C is always on in this case.
A/C PRESSURE SWITCHES
The A/C compressor is connected in series with the low-
pressure switch, high-pressure switch, and safety switch. The high-
pressure and safety switch cut power to the A/C compressor if pressure
in the A/C high-pressure circuit becomes excessive, supplying a signal
to ECM to start cooling fan.
The low-pressure switch (pressostat) turns A/C compressor on
and off to maintain pressure within limits.
AIR DISTRIBUTION CONTROL
Air distribution control is based on signals from ECC control
module, which controls the ventilation damper motor and
floor/defroster damper motor. When set to AUT (automatic) mode, the
air distribution control circuit computes air distribution based on
outside (ambient) temperature, the position of driver’s side
