HVAC Systems - Automatic: Other Chrysler LHS II

Automatic Temperature Control System

Automatic Temperature Control (ATC) system operation is activated by pressing AUTO button (ATC system ON button) and selecting temperature. (Scheme 8) Temperature control is automatic when selected temperature is 60-90°F (16-32°C). Automatic temperature control is canceled when full heat or full cool is selected, OFF button is pressed, or blower motor speed and mode are manually selected.

ATC system maintains selected temperature by controlling blower motor speed and mode setting. Temperature can be reset within specified range without affecting ATC system operation. Function display and a Light Emitting Diode (LED) in push buttons will indicate current active mode. (Scheme 8)

ATC CONTROL HEAD

ATC control head includes 12 ATC buttons, a blower motor speed control selector, function display, and the ATC in-vehicle temperature sensor. (Scheme 8)

AUTO & OFF Buttons

Pressing ATC control head AUTO button turns ATC system on. When ATC control head OFF button is pressed, ATC system is turned off.

Blower Motor Control Selector

Blower motor/fan has 14 automatic speeds controlled by blower motor power module through pulse width modulated signals from BCM. Blower motor speed can be manually controlled by rotating blower motor control selector.

Temperature Control Buttons

Temperature control buttons allow a specified interior temperature to be selected. Pressing upper button will increase temperature and pressing lower button will decrease temperature.

Mode Controls

There are 6 buttons for manual selection of air delivery mode: panel, mix, front defrost, recirculated air, floor, and bi-level. These buttons should be used when comfort or visibility in full automatic operation cannot be obtained. Manual control of air recirculation is possible only in panel, floor and bi-level modes. If recirculation air mode button is pressed during mix or defrost mode operation, recirculation air button LED will blink.

Rear Defrost Button

Rear defrost operates independently of all control modes when ignition is on. A 15-minute cycle begins and LED will illuminate when rear defrost button is pressed. After first 15-minute cycle, subsequent operations will only be 7.5-minute cycles. When ignition is turned off or rear defrost push button is pressed to OFF position, current cycle will abort. Rear defrost button operates a plug-in relay located on the back of control panel.

Scheme 8

A/C PRESSURE TRANSDUCER

A/C pressure transducer is located near condenser, screwed onto a discharge line valve. A/C pressure transducer monitors A/C system pressure. Operation of condenser fan, radiator fan and A/C compressor are supported by signals from pressure transducer.

BLOWER MOTOR POWER MODULE

Blower motor power module controls 14 blower motor speeds and a blower off signal, through pulse width modulated signals received from Body Control Module (BCM). Blower motor power module changes voltage to blower motor for different blower speeds. Blower motor power module is located on the lower right side of A/C-heater assembly. (Scheme 9)

Scheme 9

EVAPORATOR TEMPERATURE SENSOR

Evaporator temperature sensor (evaporator probe) is located on lower right side of A/C-heater assembly, at the coldest point of evaporator. (Scheme 9)

Body Control Module (BCM) monitors sensor output. Sensor is used to switch off compressor clutch before evaporator freeze-up occurs.

Evaporator temperature set point, used to turn compressor clutch off, varies with outside ambient temperature. Clutch will be turned on when evaporator temperature has increased 2.0°F (1.1°C) more than set point. See EVAPORATOR TEMPERATURE SENSOR SET POINT table.

EVAPORATOR TEMPERATURE SENSOR SET POINT

SUN LOAD SENSOR

Sun load sensor is a photo diode, located on top of the instrument panel. Sun load sensor senses level of sunlight entering vehicle. Sun load sensor helps determine optimum mode door and temperature door positions, and blower motor speed.

IN-VEHICLE TEMPERATURE SENSOR

In-vehicle temperature sensor is composed of a temperature thermistor and a sensor aspirator fan assembly. Temperature thermistor is located in ATC control head, below blower motor control selector. (Scheme 8) Sensor aspirator fan assembly is attached to the back of the ATC control head. During fan operation, passenger compartment air is drawn into sensor, over temperature thermistor. BCM measures thermistor resistance changes, calculates air temperature, and changes ATC system operation to make temperature adjustments.

DTCs will set if sensor failure is detected by BCM. Sensor aspirator fan assembly can be serviced separately. Temperature thermistor is serviced by replacing ATC control head.

In-vehicle temperature sensor will operate when ignition is turned on, even if ATC is turned off. Sensor will turn off when ignition switch is turned off after driving vehicle. If a door is opened and not closed, and ignition is not turned on, sensor will turn off about 2 minutes after door is opened. If a door is opened and closed without turning ignition on, sensor will turn off about 2 minutes after door is closed.

AMBIENT TEMPERATURE SENSOR

Ambient temperature sensor is located inside right front bumper beam, near power steering cooler. This thermistor monitors outside air temperature. BCM uses ambient temperature to adjust blower speed, temperature offsets, evaporator temperatures, and mode control. If sensor fails, battery temperature input is used as back-up.

A/C SYSTEM PERFORMANCE

1. Park vehicle out of direct sunlight. Ambient air and in-vehicle temperatures must be greater than 70°F (21°C). Connect a tachometer and compressor manifold gauge set to vehicle. Attach a thermocouple to evaporator line. Start and run engine at 1000 RPM with A/C turned off and transmission in Park, until radiator fan comes on. Allow engine to idle.
2. Close all vehicle doors and windows. Turn blower control selector fully clockwise, to high position. Set temperature to low position. Push panel mode button. Push recirculate air button. Ensure MANUAL is displayed on function display and A/C (snowflake) and recirculation symbols are also displayed.
3. Hold engine speed at 1000 RPM and ensure compressor clutch is engaged. Insert thermometer into left center A/C outlet and operate engine for 5 minutes. Compressor clutch may cycle depending on ambient air temperature.
4. When compressor clutch is engaged, compare discharged air temperature and A/C system pressure with specified temperature and pressures. See «A/C SYSTEM PERFORMANCE TEMPERATURE SPECIFICATIONS»(ref-211-S22471522192000030800000) and «A/C SYSTEM PERFORMANCE PRESSURE SPECIFICATIONS»(ref-211-S06484349302000030800000) tables. System is okay if temperature and system pressures are as specified.

A/C SYSTEM PERFORMANCE TEMPERATURE SPECIFICATIONS

A/C SYSTEM PERFORMANCE PRESSURE SPECIFICATIONS

Manifold Gauge Set Method

1. Attach clamp-on thermocouple to liquid line, as close to condenser outlet as possible. Attach manifold gauge set to high-side and low-side connectors.
2. Set parking brake, and place transaxle in Park position. Start engine and allow to idle. Set A/C controls to outside air, panel mode, full cool, and high blower speed. Turn A/C on, and open windows. Operate system for a few minutes to allow system to stabilize.
3. Place cardboard over front grille area, to block airflow through part of condenser, to set A/C pressure to 260 psi (18.3 kg/cm 2 ). This will stop cooling fans from alternating speeds and maintain constant pressure.
4. Record temperature reading at liquid line and discharge pressure reading on gauges. Compare readings with values in «REFRIGERANT CHARGE LEVEL»(ref-211-S16982840922000030800000) table.
5. Depending on system charge condition, corrections are made 2 ounces at a time. Each time a correction is made, recheck readings to ensure proper charge. Total system refrigerant capacity is 28 ounces.

REFRIGERANT CHARGE LEVEL

IN-VEHICLE TEMPERATURE SENSOR AIRFLOW CHECK

1. In-vehicle temperature sensor aspirator fan air inlet is located in ATC control head. (Scheme 8) Turn ignition on. Press ATC control head OFF button to stop ATC system airflow. Place a piece of tissue paper in front of sensor opening.
2. If paper sticks to sensor opening, in-vehicle temperature sensor aspirator fan is operating properly. If tissue paper does not stick, ensure in-vehicle temperature sensor electrical connector terminals are clean and tight.
3. If connector terminals are okay and DTC 26 is not present, replace sensor aspirator fan and recheck sensor air flow. If tissue paper still does not stick, perform «TEST 8A: ATC IN-VEHICLE TEMPERATURE THERMISTOR FAILURE»(ref-211-S35954835632000030800000).

SUN LOAD SENSOR CHECK

1. Locate sun load sensor on top of instrument panel. Ensure sensor is not shaded or covered by caps, papers, improperly adjusted windshield wipers, top cover improperly installed, or stickers installed on windshield.
2. If passenger compartment temperature cannot be maintained during sunny weather, especially during early afternoon, check sensor installation. Ensure sensor protrudes about 0.25" (6.4 mm) above instrument panel cover. If nothing is shading or covering sensor, and sensor height above instrument panel is correct, perform «TEST 13A: ATC IN-VEHICLE SUN LOAD SENSOR FAILURE»(ref-211-S38291372662000030800000) .

Note. For 3.2/3.5L applications, the passenger side headlight must be rotated out of the way to access the A/C pressure transducer.

Note. In-vehicle temperature sensor is composed of a temperature thermistor and a sensor aspirator fan assembly. Temperature thermistor is serviced as part of ATC control head. (Scheme 8) If temperature thermistor replacement is required, ATC control head must be replaced.

Note. NOTE: Retest ATC control. If ATC control still fails the paper test, then replace the ATC control and fan-motor assembly. The ATC control panel must be replaced if the part fails fault code 26 (after confirming proper wiring connections).

RECEIVER/DRIER

Note. Always install new "O" rings when replacing receiver/drier.