A/c-Heater System - Automatic: Other Hyundai Sonata IV

AUTOMATIC A/C-HEATER SYSTEM

The operation of the automatic A/C-heater system is accomplished by selecting a desirable in-vehicle temperature on A/C-heater control panel (A/C control module). (Scheme 4) Once temperature is selected, the A/C control module will maintain the specified temperature. The A/C control module includes a self-diagnostic feature that will detect electrical malfunctions and provide error codes for suspect components/circuits.

Scheme 4

AMBIENT TEMPERATURE SENSOR

This sensor is located in front of condenser fan shroud. The sensor contains a thermistor which measures outside air temperature.

BLEND DOOR ACTUATOR

The blend door actuator is located on driver's side of evaporator case. The actuator controls position of blend door based on a low current signal from the A/C control module.

Inside blend door actuator, an electronic circuit accepts the signal and positions the blend door with a small direct current (DC) motor. A potentiometer inside the blend door actuator provides a feedback signal to the A/C control module.

The blend door actuator operates based on input signals from temperature setting, in-vehicle temperature sensor, ambient temperature sensor, and thermo (engine coolant temperature) sensor.

COLD ENGINE LOCK-OUT SENSOR

The Cold Engine Lock-Out (CELO) sensor is wired to the blend door actuator and is attached to heater core inlet tube (under the actuator mounting bracket) with a spring tension clip. The sensor prevents cold air from blowing out of vents when outside air temperature is low and engine is cold. This control however is only provided when blower switch is in AUTO mode.

Until engine coolant temperature reaches 122°F (50°C) or the desired temperature becomes equal too or more than inside temperature, cold air will not blow and fan speed will be maintained at low speed. If a manual fan speed is selected, the blower motor will operate at selected speed.

IN-CAR TEMPERATURE SENSOR

The in-car temperature sensor contains a thermistor which measures passenger compartment air temperature. The sensor measures passenger compartment air temperature, changes its resistance value, and sends a corresponding voltage signal to the A/C control module.

PHOTO SENSOR

Photo (sunload) sensor is located on top of instrument panel and is visible through windshield. The photo sensor contains a photovoltaic (sunlight sensitive) diode. The solar radiation received by its light-sensitive portion generates an electrical signal which is sent to A/C control module so that solar radiation compensation can take place.

THERMO SWITCHES

Thermo switches (sensors) "A" and "B" are located on right side of radiator. If engine coolant exceeds 239°F (115°C), current flow to cooling control module will be interrupted. Cooling control will then turn off A/C compressor.

Check ambient temperature sensor resistance at increasing temperatures. Sensor resistance should decrease as temperature increases. At 77°F (25°C), resistance should be 35.05-39.55 k/ohms.

Connect a voltmeter to blend door actuator terminals No. 1 and 6. (Scheme 5) Press temperature control switch up and down, and ensure voltage changes. At 63°F (17°C), voltage should be 0.15-0.45. At 90°F (32°C), voltage should be 4.55-4.85. Replace blend door actuator if voltage is not as specified.

Scheme 5

BLOWER CONTROL

1. Connect a voltmeter across blower motor terminals. Using another voltmeter, connect positive voltmeter lead to Yellow/Red wire terminal of power transistor. Connect negative voltmeter lead to Blue/Black wire terminal of power transistor.
2. Voltage at power transistor should increase with an increase in blower motor speed, until high blower relay works (high speed). Blower motor voltage should be as specified in «BLOWER MOTOR VOLTAGE»(ref-322-S33551278312000030800000) table. If blower control is not as specified, repair circuit, replace power transistor, or blower motor as necessary.

BLOWER MOTOR VOLTAGE

Place cold engine lock-out sensor in water. Heat water and check cold engine lock-out sensor resistance. At 77°F (25°C), resistance should be 9.5-10.5 k/ohms. At 140°F (60°C), resistance should be 2.26-2.86 k/ohms. If resistance is not as specified, replace sensor.

Check in-car temperature sensor resistance at increasing temperatures. Sensor resistance should decrease as temperature increases. At 77°F (25°C), resistance should be 29.64-30.36 k/ohms.

1. Using a jumper wire, connect positive battery terminal to photo sensor terminal No. 1. Connect a voltmeter to remaining terminal and battery negative terminal (ground). (Scheme 6)
2. In the dark, measure voltage output from sensor. Using a 60-watt bulb placed within 6" (40 cm) of sensor, measure voltage output again. Ensure voltage output is higher than in the dark. If voltage output is not as specified, replace photo sensor.

Scheme 6

THERMO SWITCH

Place thermo switch in water. Heat water and check thermo switch continuity. Below 239°F (115°C), continuity should exist. Above 239°F (115°C), no continuity should exist. If continuity is not as specified, replace thermo switch.