A/c-Heater System - Automatic: Other Volvo 850 I

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 30 MPH; or when heater fan is off and recirculation is on.

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 cuts 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 temperature control dial, and engine coolant temperature.

At low outside temperatures, the ECC control module selects floor/defrost setting, with a slight amount of bi-level air if sunshine is present. If outside temperature is between 50-66°F (10-19°C), a varying degree of bi-level air is selected. At temperatures greater than 68°F (20°C), all air is directed to instrument panel vents.

The ventilation air distribution setting is selected if driver's side control panel is set for maximum cooling. The floor/defrost setting is selected if maximum heating is selected.

The defrost air distribution setting is selected if engine is cold and outside and interior temperatures are also low. This changes to varying degrees of floor/defrost air distribution as engine coolant temperature increases. The transition from defroster to floor/defroster setting takes place more quickly in sunshine.

AIR TEMPERATURE SENSORS & SOLAR SENSOR

Two interior temperature sensors and 2 duct temperature sensors are required for individual temperature control of driver's and passenger's sides. Each interior temperature sensor incorporates a fan which draws air through sensor.

The resistance of the air temperature sensors decreases as temperature increases. The solar sensor, combined with the theft alarm diode, is a photodiode which generates a current when exposed to solar radiation.

DAMPER MOTORS

The temperature control damper motors, recirculation damper motor, floor/defroster damper motor, and ventilation damper motor are all identical, but their control range varies according to the damper being controlled.

The damper motors have a position sensor to enable the ECC control module to determine damper position, learn the damper limit positions, and to detect any fault in damper motor. The ventilation damper is operated by damper motor through 2 gear segments, one fitted to damper motor shaft and the other on ventilation damper shaft.

FAN CONTROL

Heater (blower motor) fan speed is variably controlled by ECC output (power) stage in response to signals from ECC control module. The ECC control module digital control signals vary in length according to required fan speed.

The ECC output stage has an electronic unit which receives the digital control signals and converts them to voltage. If there is no control signal or the fan is disabled, the ECC output stage sends a diagnostic signal to inform the ECC control module of the fault.

If fan speed control lever is set to AUT (automatic) mode, fan speed is influenced by the position of driver's side temperature control dial, driver's side interior temperature sensor, vehicle speed, and engine coolant temperature.

The highest fan speed is selected if driver's side temperature control dial is set to maximum or minimum cooling or heating. The greater the difference between the desired and actual temperatures, as sensed by the driver's side temperature sensor, the higher the fan speed.

As vehicle speed increases, the fan speed will be reduced to maintain a constant airflow throughout the passenger compartment. When heating the passenger compartment after starting a cold engine, the fan speed is gradually increased as engine coolant temperature rises.

RECIRCULATED AIR MODE

The ECC control module selects recirculated air mode only for a combination of cooling and high outside temperature, provided that

1. 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.
2. 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.

Controlling A/C Relay

Enter control code 1-1-1 by pressing button on diagnostic unit 3 times, with a short pause in between to allow LED to come on again. ECC control module will now switch A/C relay on and off 5 times (10 seconds on, 10 seconds off), switch A/C compressor on and off, and turn control panel A/C indicator on and off. If A/C relay does not respond as indicated, check A/C relay. See A/C RELAY CHECK under TESTING.

Self-Adjustment Of Damper Motor Limit Positions

1. Turn ignition on. Place fan (blower motor) lever in manual mode. Turn function selector to AUT (automatic). Ensure system is in TEST MODE 4.
2. Enter control code 9-9-9 by pressing button on diagnostic unit 9 times in quick succession. Enter each of the 9 series 3 times, with a short pause in-between to allow LED to come on again. ECC control module is now ready to adjust damper motor limit positions automatically.
3. Wait about 10 seconds for fan to start. Turn ignition off to exit TEST MODE 4. Turn ignition on. AC OFF and REC indicator on A/C control panel should flash. Drive car for a few minutes at speeds greater than 20 MPH.
4. Stop car and turn engine off, but leave ignition on for at least 2 minutes to enable ECC control module to store all values. Start TEST MODE 1 and record DTCs. If DTC 1-1-1 appears, self-adjustment is complete. If DTC 5-1-1 appears, self-adjustment is not complete.

Changing Data Transmission Speed/Rate From ECC Control Module

To On-Board Diagnostic Unit

Enter desired control code (3-1-1 or 3-1-2) by pressing button on diagnostic unit "A", with a short pause in-between to allow LED to come on again. System always starts at normal speed unless another option is selected. If another option was selected, system will revert to normal speed each time ignition is turned off.

ERASING CODES

1. All codes must be displayed at least once before they can be erased. To erase codes, ensure selector cable is connected to terminal No. 1 of diagnostic unit "B". see scheme 2 Press and hold diagnostic button for at least 5 seconds. LED should illuminate 3 seconds after button is released.
2. Press and hold diagnostic button for a minimum of 5 seconds more. When button is released, LED should go out. Ensure codes have been erased by pressing diagnostic button once. If display shows 1-1-1, codes have been erased/cleared. If a DTC will not erase/clear, perform that particular code's diagnosis again.

AIR BAG TESTS

A/C System Performance

1. Ensure compressor drive belt is okay, fan motor runs at all speeds, and that temperature vents shut completely with temperature switch in full cooling position.
2. Ensure that all air comes from panel vents with mode control on vent position, recirculation motor is working, and condenser fan and cooling fan are working.
3. Start and warm engine to normal operating temperature. Ensure compressor clutch engages when A/C is turned on. Set temperature switch to full cold position, place mode control to vent position, turn on recirculate air switch and blower fan switch high speed.
4. Close engine hood, doors and windows. Run engine at 1500-1600 RPM. Place thermometer in one of the center panel vents. Allow system to stabilize for at least 8 minutes. Check temperature in center panel vent. See «A/C SYSTEM PERFORMANCE SPECIFICATIONS»(ref-13719-S38979970012001032700000) .

A/C SYSTEM PERFORMANCE SPECIFICATIONS (1)

A/C Relay Check

Remove relay. Connect battery positive lead to relay terminal No. 1 and negative lead to relay terminal No. 3. Continuity should be present between relay terminals No. 2 and 4. see scheme 4-9 and see scheme 16. If continuity is not present, replace relay.

On-Board Diagnostic Unit Check

1. Turn ignition on. Press button on diagnostic unit "A". see scheme 2 LED should illuminate. If LED does not illuminate, go to next step. If LED illuminates, but no code(s) is(are) present, go to step 4).
2. Turn ignition off. Remove connector from underside of diagnostic unit "A". Connect voltmeter between terminal No. 4 of diagnostic unit "A" and ground. Turn ignition on. Battery voltage should be present. If battery voltage is present, go to next step. If battery voltage is not present, check fuse No. 33 or open circuit between fuse block and terminal No. 4.
3. Turn ignition off. Connect ohmmeter between terminal No. 8 of diagnostic unit "A" and ground. Continuity should exist. If continuity exists, replace diagnostic unit and retest. If continuity does not exist, check ground connection.
4. Turn ignition off. Disconnect selector cable from diagnostic unit "B". Turn ignition on. Connect voltmeter between terminal No. 1 of diagnostic unit "B" and ground. Voltage should be about 10 volts. If voltage is as specified, replace diagnostic unit. If voltage is not as specified, check for open or shorted circuit between ECC control module and terminal No. 1 of diagnostic unit "B".

Pin Voltage Tests

Note. Perform all voltage tests using Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance.

Pin voltage chart is supplied to reduce diagnostic time. Checking pin voltage at ECC control module determines whether it is receiving or transmitting proper voltage signals. Charts may also help determine if control unit wiring harness has short or open circuit.

ECC CONTROL MODULE PIN ASSIGNMENTS CONNECTOR "A" (1)

ECC CONTROL MODULE PIN ASSIGNMENTS CONNECTOR "B" (1)

ECC CONTROL MODULE PIN ASSIGNMENTS CONNECTOR "C" (1)

Solar Sensor

1. Connect test unit to ECC control module. Check ground circuits. See DTC 1-2-1, OUTSIDE TEMP. SENSOR CIRCUIT SHORTED TO GROUND. If ground circuits are okay, go to next step.
2. Turn ignition on. Aim a light source at solar sensor. Connect voltmeter between test unit pins No. 51 and 56 and record voltage. Cover solar sensor and read voltage again. (Scheme 37) Voltage should vary by a few millivolts. The higher the intensity, the lower the voltage. If sensor does not operate as specified, there is an open circuit or short to ground in wire or solar sensor.

Scheme 37

Speedometer Signal

1. Raise and support front of vehicle. Perform TEST MODE 2 under FAULT DIAGNOSTICS. ECC control module should respond to vehicle speed signal with Code 1-1-3. ECC control module will continue to flash code even once TEST MODE 2 is activated. If Code 1-1-3 does not appear, turn ignition off. Cover solar sensor. Turn ignition on. Start TEST MODE 2. Let car wheels turn freely. Open throttle.
2. If no acknowledgment code appears after several attempts, there may be a problem with vehicle speed signal impulse sensor in ignition system, instrument panel, or wiring.
3. Check if speedometer operates. If speedometer does not operate, a fault may be present in vehicle speed signal impulse sensor, ignition system, instrument cluster, or wiring. If speedometer does operate, check for open circuit in instrument cluster wiring.

CONDENSER

Note. When replacing condenser, always replace "O" rings and snap-on connections.

DASHBOARD

Note. Dashboard consists of 5 main sections: upper frame, lower frame (left and right), defroster duct and dashboard cover. Except for dashboard cover, all the main sections are glued together and cannot be separated.

DUCT TEMPERATURE SENSOR

Note. The duct temperature sensor is located in the driver's or passengers side ventilation duct.

Scheme 38

Scheme 39

Scheme 40

1. Turn ignition off.
2. Remove radio.
3. Insert hand underneath control module. Push up locking button on underside of control module. (Scheme 38)
4. Push control module loose from behind (from rear corner).
5. Remove control module.
6. Disconnect 3 connectors from control module. Remove control unit.
7. Remove passenger side sound wall. (Scheme 39)
8. Remove 4 screws from glove compartment. (Scheme 39)
9. Remove 4 screws from glove compartment panel. Remove glove compartment. (Scheme 39)
10. Remove connector from duct temperature sensor. (Scheme 40)
11. Remove duct temperature sensor by cutting off tie and pulling duct temperature sensor downwards.
12. To install, reverse removal procedures.

HEATER CORE