Volvo 850. Manual

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

Volvo 850. Manual - part 58