A/c-Heater System - Automatic Mazda 929 HC

A/C SYSTEM SPECIFICATIONS

A/C SYSTEM SPECIFICATIONS

DESCRIPTION & OPERATION

AUTOMATIC CLIMATE CONTROL SYSTEM

The automatic climate control system comes on when "AUTO" push button is depressed. The system will activate A/C-heater system and mix a combination of heated/air conditioned air as necessary to reach desired temperature. Temperature setting dial allows temperature to be set between 68°F (20°C) and 86°F (30°C).

Depending on desired temperature, the system also automatically selects fresh, 1/3 fresh or recirculate (passenger compartment) air. Manual operation of fresh/recirculated air can be obtained by depressing appropriate push button. (Scheme 1)

Depressing the defrost push button directs treated air to windows and the system continues to control set temperature. Depressing the "AUTO" push button returns system to normal operation. Depressing "OFF" push button turns the system off.

When "ECO" (economy) is used, the compressor will stay off for longer time periods. This setting allows the compressor to cycle less using a second range of temperatures detected in the evaporator.

Scheme 1

Passenger Compartment Temperature (PCT) Sensor

The passenger compartment temperature sensor is located below the glove box. This sensor detects passenger compartment temperature and sends signals to the auto control unit.

Duct Sensor

The duct sensor is located inside the evaporator case. This sensor detects temperature changes at evaporator outlet caused when compressor is cycling or when intake door changes between inside and outside air intake. Signals from duct sensor are then input to the automatic control unit.

Ambient Temperature Sensor

The ambient temperature sensor is mounted on the center grille support. This sensor detects ambient temperature of outside air and sends signals to the automatic control unit.

Sun Sensor

The sun sensor is located on driver's side of dash panel. Strong sunlight coming through windows creates a warmer than true temperature inside the vehicle. The sun sensor allows the automatic climate control system to compensate for this effect.

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The automatic climate control system has a built-in self-diagnostic feature. Self-diagnostic function checks sensors on input side and actuators on output side. Indicator lights on control panel will come on to direct technician to appropriate circuit test. See SELF-DIAGNOSTIC INDICATOR LIGHTS TABLE . Perform additional test as indicated in chart(s). See AUTOMATIC A/C CONTROL SELF-DIAGNOSTIC TEST in this article.

SELF-DIAGNOSTIC INDICATOR LIGHTS

AMBIENT TEMPERATURE, DUCT & PCT SENSORS

Disconnect sensor's connector and measure resistance between the 2 terminals. If resistance is not 2900-3100 ohms with an ambient temperature of 77°F (25°C), replace sensor.

1. Disconnect sensor connector and measure the resistance between the 2 terminals. (Scheme 24) With negative probe of ohmmeter on terminal No. 1 and positive probe on terminal No. 2, reading should be less than 200 ohms. With probes reversed, reading should be more than 10,000 ohms.
2. Set circuit tester at 3 milliamp range. Hold at least a 60 watt light, 6 inches from sensor. Measure current between the 2 terminals. If current measures less than.2 milliamps, replace sensor.

Scheme 24

COOLANT THERMOSWITCH

Note. This thermoswitch is not to be confused with any type input for engine control operation. It is only an input for climate control system operation.

Remove thermoswitch from heater unit. Place thermoswitch in plastic bag and insert plastic bag and thermoswitch in ice water. Using an ohmmeter, check that there is continuity when temperature is below 41°F (5°C). Remove thermoswitch from ice water and check that there is no continuity when temperature exceeds 59°F (15°C). Replace thermoswitch if continuity is not as specified.

POWER TRANSISTOR

1. Using an ohmmeter, check continuity between terminals in order. (Scheme 25) Connect negative lead of ohmmeter to terminal "A" and positive lead to terminal "C". Connect negative lead of ohmmeter to terminal "A" and positive lead to terminal "B". There should be continuity.
2. Connect negative lead of ohmmeter to terminal "C" and positive lead to terminal "A". There should be no continuity. Connect negative lead of ohmmeter to terminal "B" and positive lead to terminal "A". There should be no continuity.

Scheme 25

4-Terminal

Using an ohmmeter, measure resistance between relay terminals No. 1 and 2. (Scheme 26) Resistance should be between 120-140 ohms. Apply 12 volts across terminals No. 1 and 2. Continuity should now be present between relay terminals No. 3 and 4.

6-Terminal

Using an ohmmeter, measure resistance between relay terminals No. 5 and 6. (Scheme 26) Resistance should be between 60-80 ohms. Apply 12 volts across relay terminals No. 5 and 6. Continuity should now be present between relay terminals No. 3 and 4, and terminals No. 1 and 2.

Scheme 26

BLOWER SWITCH

Turn ignition on. Using a DVOM, measure voltage between terminals No. 14 and 2 of IA connector. Connector IA is located behind control panel. (Scheme 27) With blower switch off, voltage should be zero. As blower switch is gradually increased toward "MAX", voltage will gradually increase to.5 volt. Measure voltage between IA connector terminals No. 14 and 7. Voltage should be.5 volt.

TEMPERATURE CONTROL LEVER

Turn ignition on. Using a DVOM, measure voltage between IA connector terminals No. 14 and 1. Connector IA is located behind control panel. (Scheme 27) With temperature lever on lowest setting, voltage should be zero. As temperature lever is gradually increased toward highest setting, voltage will gradually increase to.5 volt. Measure voltage between IA connector terminals No. 14 and 7. Voltage should be.5 volt.

Scheme 27

Removal

1. Disconnect negative battery terminal. Disconnect compressor clutch connector. Slowly discharge refrigerant from A/C system using approved refrigerant recovery/recycling equipment. DO NOT allow refrigerant to escape too fast, as refrigerant oil will be drawn out of system.
2. Disconnect suction and discharge hoses from A/C compressor. Plug all openings. Remove idler pulley bolts, and remove drive belt. Remove compressor mounting bolts, nuts and A/C compresssor.

Installation

To install, reverse removal procedure. Adjust drive belt tension, charge A/C system, and check system performance.

1. Disconnect negative battery cable. Slowly discharge refrigerant from A/C system using approved refrigerant recovery/recycling equipment. DO NOT allow refrigerant to escape too fast, as refrigerant oil will be drawn out of system.
2. Remove front grille and air seal cover. Remove receiver-drier and bracket. Disconnect refrigerant lines from condenser. Remove 2 bolts and 2 nuts mounting condenser. Remove condenser.

To install, reverse removal procedure. If new condenser is being installed, add 1 oz. (30 cc) of refrigerant oil. Charge A/C system and check system performance.

1. Disconnect negative battery cable. Disconnect pressure switch lead wire. Slowly discharge refrigerant from A/C system using approved refrigerant recovery/recycling equipment. DO NOT allow refrigerant to escape too fast, as refrigerant oil will be drawn out of system.
2. Disconnect 2 liquid lines from receiver-drier. Plug all openings. Remove receiver-drier from bracket.

To install, reverse removal procedure. If a newreceiver-drier is being installed, add .3 oz. (10 cc) of refrigerant oil. Charge A/C system and check system performance.

1. Disconnect negative battery cable. Slowly discharge refrigerant from A/C system using approved refrigerant recovery/recycling equipment. DO NOT allow refrigerant to escape too fast, as refrigerant oil will be drawn out of system.
2. Disconnect suction pipe and liquid line. Plug all openings. Remove grommets from expansion valve. Remove drain hose. Remove dash lower panel and glove box.
3. Remove blower duct. Remove sealing plates from both sides of unit. Disconnect A/C wiring harness. Remove 2 nuts attaching evaporator unit and remove unit. (Scheme 28)

To install, reverse removal procedure. Charge A/C system and check system performance.

Removal & Installation

Use evaporator unit removal and installation procedure to remove/install expansion valve. See EVAPORATOR HOUSING ASSEMBLY in this article.

Scheme 28

Mazda 929 Automatic A/C-Heater System Wiring Diagram. Scheme 29

See also:
• SELF-DIAGNOSTIC INDICATOR LIGHTS TABLE