Air conditioning system malfunctions (Discovery 1)

Malfunction	Cause	Elimination
A. The heater fan does not work or the fan speed is low.	1. Low supply voltage. 2. The fuse or relay is faulty. 3. Poor electrical contact. 4. The switch is faulty. 5. Defective electric motor bearings. 6. Break in the electric motor winding. 7. Wear of fan motor brushes. 8. Drive shaft is bent. 9. Defective resistors.	1. Check the voltage. 2. Check and replace if necessary. 3. Check the wiring and connectors. 4. Replace the switch. 5. Replace. 6. Replace. 7. Replace. 8. Repair or replace. 9. Replace.
Q. The compressor clutch does not engage.	1. Low supply voltage. 2. The fuse or relay is faulty. 3. Defective thermostat or pressure switch. 4. Open or short circuit of the clutch winding. 5. Bearing seizure (constant mesh clutch). 6. Problems with refrigerant pumping (increased compressor drive power is required).	1. Check the voltage. 2. Check and replace if necessary. 3. Check and replace if necessary. 4. Replace. 5. Replace. 6. Repair.
C. Compressor clutch noise.	1. Incorrect installation of the coupling. 2. Incorrect tension of the compressor drive belt. 3. Loss of tightening of compressor fasteners. 4. Incorrect installation of the clutch bearing. 5. Low supply voltage. 6. Resistance to clutch rotation. 7. Oiling of the clutch friction linings. 8. Clutch slippage. 9. Compressor overload or blockage. 10. Icing.	1. Repair. 2. Adjust the tension. 3. Tighten the mounting bolts. 4. Replace the coupling. 5. Check the wiring. 6. See B5. 7. Check the compressor seals. 8. See C5, check the clearance in the coupling. 9. Replace or repair the compressor. 10. Check the suction line, expansion valve and receiver-drier.
D. Condenser vibration.	1. Incorrect installation of the electric motor/fan. 2. Dirt on the fan blades. 3. Wear of electric motor bearings.	1. Check the supports. 2. Wash the blades. 3. Replace.

Air conditioning system malfunctions

The duration of the cooling cycle of the air in the cabin depends on many factors: the temperature and humidity of the ambient air, the setting of the desired air temperature level in the cabin (thermostat adjustment), air conditioning compressor speed, air conditioning system tightness, etc. If all factors remain approximately constant, but the time it takes to reach the desired temperature increases sharply, there are problems with the air conditioning system.

Start troubleshooting by checking:

• 1. Compressor drive belt tension.
• 2. Operation of the compressor drive clutch.
• 3. Operation of the condenser fan.
• 4. Condition of the condenser cooling tubes and fins.

During normal operation of the air conditioning system, a few minutes after it is turned on:

• 1. High pressure lines must be hot.
• 2. Low pressure lines must be cold.
• 3. The inlet and outlet pipes of the receiver-dryer must have the same temperature. Different temperatures of the tubes indicate that the dehumidifier is blocked.
• 4. Frost at the inlet of the expansion valve indicates a faulty valve or a large amount of moisture in the system.
• 5. The air temperature after the evaporator increases with increasing humidity of the surrounding air.

Malfunction	Cause	Elimination
A. High refrigerant outlet pressure.	1. Excess refrigerant. 2. Air in the system. 3. The condenser tubes are clogged. 4. Condenser fan motor defective. 5. Supply voltage of the condenser fan motor.	1. Recharge the system. 2. Recharge the system. 3. Rinse the condenser. 4. Replace. 5. Check the wiring.
B. Low refrigerant outlet pressure.	1. Lack of refrigerant (air bubbles are visible in the viewing window). 2. Defective compressor gasket or leaky valves. 3. Compressor defect.	1. Recharge the system, check for leaks. 2. Replace the gasket or valve, install a new dehydrator. 3. Replace the compressor.
C. High refrigerant inlet pressure.	1. Poor tension of the compressor drive belt. 2. Icing on the suction line. 3. The expansion valve is stuck in the open position. 4. Defective compressor gasket or leaky valves. 5. Blocking the receiver-dryer.	1. Adjust the belt tension. 2. Check the fastening of the temperature sensor's sensitive element: it should fit tightly to the surface of the copper inlet tube. 3. Replace the valve. 4. Replace the gasket or valve, install a new dehydrator. 5. Install a new dehumidifier.
D. Low refrigerant inlet pressure.	1. Expansion valve temperature defect. 2. The expansion valve is stuck in the closed position. 3. Ice has formed in the expansion valve nozzle (the valve outlet is covered with frost, the inlet is not; the system works periodically). 4. Dirty surface of the evaporator grille. 5. Defective heater fan or fan speed switch.	1. Heat the sensing element with your hand: the pressure should quickly rise to 1.4 bar. If not, replace the valve. 2. See C2 and C3. 3. Install a new receiver, recharge the system. 4. Wash the grill. 5. Eliminate.
E. Noise from the expansion valve.	1. Lack of refrigerant.	1. Check the system for leaks, recharge
F. Insufficient cooling.	1. Defective expansion valve. 2. Lack of refrigerant. 3. Compressor defect.	1. See C2, C3, D1 and E. 2. See B1 and E. 3. See B2 and B3.
G. Compressor drive belt slippage.	1. Belt tension. 2. Increased outlet pressure. 3. Misalignment of compressor drive pulleys or belt wear. 4. Pulley defect. 5. Seizures in the compressor.	1. Adjust the tension. 2. See A1-A4 and C6. 3. Repair. 4. Repair. 5. Replace the compressor.
H. Engine noise and/or vibration.	1. Loosening of the support mounting bolts. 2. Broken support bracket. 3. Loose flywheel or clutch mounting bolts. 4. Defective bearing of the idler pulley in the belt drive. 5. Defective installation of the pulley on the nose of the crankshaft. 6. Compressor bearing defect. 7. Loosening the mounting bolts of the attachments. 8. Increased pressure at the compressor outlet. 9. Lack of lubrication in the compressor.	1. Tighten. 2. Replace. 3. Tighten. 4. Replace. 5. Install correctly. 6. Replace. 7. Tighten. 8. See A1, A2, A3, A4 and C6. 9. Check the oil level.