Automatic Heating & A/c: Other Daewoo Nubira II

Controller

The operation of A/C system is controlled by switches on control head. This console-mounted heating and ventilation system contains following knobs and display

Temperature Control Push Knobs

1. Raise temperature of air entering vehicle by pressing top switch, with red arrow pointing upward.
2. Lower temperature by pressing bottom switch, with blue arrow pointing downward.
3. Actuate air mix door by an electric motor.
4. Vary mix of air passing through heater core with air bypassing core. Each press of a switch changes set temperature by increments of 1°F (.5°C). This is shown in temperature window on function display.

Function Display

This is an LCD display indicating status of control settings selected. Starting from left end of display, sections are as follows

1. Temperature Setting - Indicates temperature set with temperature control knob.
2. Auto Status - Indicates whether system is operating in full auto mode or manual mode.
3. Defroster Icon - Indicates manual selection of full defrost mode.
4. Mode - Indicated by icon, mode chosen by system in auto (or by operator in manual) is shown by a illumination arrow indicating air path.
5. A/C - A snowflake icon indicating whether A/C is ON or OFF.
6. Fan Speed - Indicates fan speed by illuminating a bar based on segment at front, for low speed, and adding additional segments in order up to fifth, for high speed.

Eight Additional Push Knobs

1. Full Defrost - Causes mode motor, to direct all air to windshield and aide window outlets for maximum defrosting.
2. Air Intake - Switches between fresh air intake, default, and recirculating air. Airflow arrows on display indicate mode in effect.
3. Full Auto Switch - Maintains set temperature automatically. In this mode, Fully Automatic Temperature Control (FATC) system controls following: The air mix door motor. The mode door motor. The blower motor speed. The inlet air door motor. A/C ON/OFF.
4. OFF Switch - Turns automatic air conditioning and fan control off.
5. Mode Switch - Allows manual selection of airflow direction. Selection is shown on function display. Each time mode switch is pressed, next function is displayed.
6. A/C Switch - Allows manual selection and control of air conditioning function.
7. Fan Control Switch - Allows manual selection among 5 fan speeds.
8. Defogger Switch - Turns on electric defogging heater in rear window and outside rearview mirrors, if vehicle is equipped with heated mirrors.

Pressure Transducer

Pressure transducer switching incorporates functions of high-pressure and low-pressure cutout switches along with fan cycling switch. The pressure transducer is located in high-side liquid refrigerant line behind right strut tower, between right strut tower and fire wall. The output from this pressure transducer goes to Electronic Control Module (ECM), which controls compressor function based on pressure signal.

Wide-Open Throttle (WOT) Compressor Cutoff

During full-throttle acceleration, Throttle Position Sensor (TPS) sends a signal to ECM, which then controls compressor clutch.

High RPM Cutoff

As engine RPM approaches maximum limit, ECM will disengage compressor clutch until engine slows to a lower RPM.

Compressor

All compressors are belt-driven from engine crankshaft through compressor clutch pulley. The compressor pulley rotates without driving compressor shaft until an electromagnetic clutch coil is energized. When voltage is applied to energize clutch coil, clutch plate and hub assembly are drawn rearward toward pulley. The magnetic force locks clutch plate and pulley together as one unit to drive compressor shaft.

As compressor shaft is driven, it compresses low-pressure refrigerant vapor from evaporator into a high-pressure, high temperature vapor. The refrigerant oil which is used to lubricate compressor is carried with refrigerant.

Pressure Relief Valve

The compressor is equipped with a pressure relief valve which is placed in system as a safety factor. Under certain conditions, refrigerant on discharge side may exceed designed operating pressure. To prevent system damage, valve is designed to open automatically at 3171 to 4137 kPa (460 to 600 psi) in an R-134a system. Conditions that might cause this valve to open, such as a defective pressure transducer or an inoperative cooling fan, etc., should be corrected. The refrigerant oil and refrigerant should be replaced, as necessary.

Condenser Core

The condenser assembly in front of radiator consists of coils which carry refrigerant and cooling fins that provide rapid transfer of heat. The air passing through condenser cools high-pressure refrigerant vapor and causes it to condense into a liquid.

Expansion Valve

The expansion valve is located with evaporator core, inside heater/air distributor case under instrument panel. The expansion valve can fail in 3 different positions: open, closed, or restricted.

An expansion valve that fails in open position will result in a noisy A/C compressor or no cooling. The cause can be a broken spring, a broken ball, or excessive moisture in A/C system. If spring or ball are found to be defective, replace expansion valve. If excessive moisture is found in A/C system, recycle refrigerant.

An expansion valve that fails in closed position will result in low suction pressure and no cooling. This may be caused by a failed power dome or excessive moisture in A/C system. If power dome on expansion valve is found to be defective, replace expansion valve. If excessive moisture is found in A/C system, recycle refrigerant. A restricted expansion valve will result in low suction pressure and no cooling. This may be caused by debris in refrigerant system. If debris is believed to be cause, recycle refrigerant, replace expansion valve, and replace receiver-dryer.

Evaporator Core

The evaporator is a device which cools and dehumidifies air before it enters vehicle. High-pressure liquid refrigerant flows through expansion tube (orifice) and becomes a low-pressure gas in evaporator. The heat in air passing through evaporator core is transferred to cooler surface of core, which cools air. As process of heat transfer from air to evaporator core surface is taking place, any moisture (humidity) in air condenses on outside surface of evaporator core and is drained off as water.

Receiver-Dryer

The sealed receiver-dryer assembly is connected to condenser outlet pipe. It acts as a refrigerant storing container, receiving liquid and some vapor and refrigerant oil from evaporator. At bottom of receiver-dryer is desiccant, which acts as a drying agent for moisture that may have entered system. An oil bleed hole is located near bottom of receiver-dryer outlet pipe to provide an oil return path to compressor. The receiver dryer is serviceable only as an assembly.

Heater Core

The heater core heats air before it enters vehicle. Engine coolant is circulated through core to heat outside air passing over fins of core. The core is functional at all times and may be used to temper conditioned air in A/C mode as well as in heat or vent mode.

HANDLING REFRIGERANT

Air conditioning systems contain refrigerant. This is a chemical mixture which requires special handling procedures to avoid personal injury. Always wear goggles and wrap a clean cloth around fittings, valves and connections when performing work that involves opening refrigerant system. Do not weld or steam clean on or near any vehicle installed air conditioning lines or components.

All refrigerant drums are shipped with a heavy metal screw cap. The purpose of cap is to protect valve and safety plug from damage. It is good practice to replace cap after each use of drum. If it is necessary to transport or carry any container of refrigerant in a vehicle, do not carry it in passenger compartment.

HANDLING OF REFRIGERANT LINES & FITTINGS

Note. Using too low or too high a torque when tightening a fitting can result in loose joints or deformed joint parts. Both conditions can result in refrigerant leakage: Keep all metal tubing lines free of dents or kinks. Any line restrictions will cause loss of system capacity. Never bend a flexible hose line to a radius of less than 4 times diameter of hose. Never allow a flexible hose line to come within 2-1/2" (63.5 mm) of exhaust manifold. Inspect flexible hose lines regularly for leaks or brittleness. Replace flexible hose lines with new lines if there are signs of deterioration or leaking. Discharge refrigeration system of all refrigerant before disconnecting any fitting in refrigeration system. Proceed very cautiously regardless of gauge readings. Open fittings very slowly. Keep your face and your hands away from fitting so that you will not be injured if there happens to be liquid refrigerant in line. If pressure is noticed when loosening a fitting, allow pressure to bleed off as described in "Discharging, Adding Oil, Evacuating and Charging Procedures for A/C System" in this section. Cap or tape any refrigerant line immediately after it is opened. This will prevent entrance of moisture and dirt, which can cause internal compressor wear or plugged lines in condenser, evaporator core, expansion valve or compressor inlet screens. NOTE: Use 3 proper wrenches to connect O-ring fittings. Back up opposing fitting to prevent distortion of connecting lines or components. Back up both swaged fitting on flexible hose connections and coupling to which it is attached with 2 wrenches to prevent turning fitting and damaging ground seat. Keep O-rings and seats in perfect condition. A burr or a piece of dirt may cause a refrigerant leak. Dip new O-rings in clean PolyAlkalene Glycol (PAG) refrigerant oil before installation.

COMMON HVAC COMPONENTS

For following components, also used in non-automatic systems, see appropriate HEATING & VENTILATION or MANUAL HEATING & A/C SYSTEM article

1. Blower Motor
2. Heater Hoses
3. A/C Pressure Transducer
4. Compressor-To-Condenser Hose
5. Compressor
6. Condenser
7. Evaporator-To-Compressor Pipe
8. Evaporator-To-Receiver/Dryer Pipe
9. Receiver/Dryer
10. A/C Expansion Valve
11. Evaporator Core

V5 COMPRESSOR

Note. For overhaul procedures for the following components, see MANUAL HEATING & A/C SYSTEM article.

1. Clutch Coil
2. Clutch Plate & Hub Assembly
3. Clutch Rotor & Bearing
4. Control Valve Assembly
5. Cylinder-To-Front Head O-Ring
6. Leak Testing (External)
7. Pressure Relief Valve
8. Rear Head, Casket, Valve Plate, Reed Plate, & O-Ring
9. Shaft Seal Replacement