Pressure Diagnosis

WARNING: This page is about a different car, the 2004 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.

PRESSURE DIAGNOSIS

Condition	Possible Causes	Correction
Rapid A/C compressor clutch cycling (ten or more cycles per minute).	1. Low refrigerant system charge.	1. See DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required.
	2. Faulty Evaporator Temperature Sensor.	2. See EVAPORATOR TEMPERATURE SENSOR . Test the Evaporator Temperature Sensor and replace, if required.
	3. Faulty Powertrain Control Module (PCM).	3. Refer to POWERTRAIN DIAGNOSTIC PROCEDURES for testing of the PCM. Test the PCM and replace, if required.
	4. Faulty A/C Pressure Transducer.	4. See A/C PRESSURE TRANSDUCER . Test the A/C Pressure Transducer and replace, If required.
Equal pressures, but the A/C compressor clutch does not engage.	1. No refrigerant in the refrigerant system.	1. See DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required.
	2. Faulty fuse.	2. Check the fuses in the Power Distribution Center and the junction block. Repair the shorted circuit or component and replace the fuses, if required. Refer to SYSTEM WIRING DIAGRAMS .
	3. Faulty A/C compressor clutch coil.	3. See A/C COMPRESSOR CLUTCH/COIL . Test the A/C compressor clutch coil and replace, if required.
	4. Faulty A/C compressor clutch relay.	4. See A/C COMPRESSOR CLUTCH RELAY . Test the A/C compressor clutch relay and relay circuits. Repair the circuits or replace the relay, if required.
	5. Improperly installed or faulty evaporator temperature sensor.	5. See EVAPORATOR TEMPERATURE SENSOR . Test the evaporator temperature sensor and replace if required.
	6. Faulty A/C pressure transducer.	6. See A/C PRESSURE TRANSDUCER . Test the A/C Pressure Transducer and replace, if required.
	7. Faulty A/C-heater control.	7. Refer to A/C HEATER CONTROL . Test the control and replace, if required.
Normal pressures, but A/C Performance Test air temperatures at center panel outlet too high.	1. Excessive refrigerant oil in system.	1. See REFRIGERANT OIL . Recover the refrigerant from the refrigerant system and inspect the refrigerant oil content. Restore the refrigerant oil to the proper level, if required.
	2. Blend door actuator improperly installed or faulty.	2. See BLEND DOOR ACTUATOR . Inspect the actuator for proper operation and replace, if required.
	3. Blend door inoperative or sealing improperly.	3. See BLEND DOOR ACTUATOR . Inspect the blend door for proper operation and sealing Repair if required.
The low side pressure is normal or slightly low, and the high side pressure is too low.	1. Low refrigerant system charge.	1. See DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required.
	2. Refrigerant flow through the A/C accumulator is restricted.	2. See ACCUMULATOR . Replace the restricted A/C accumulator, if required.
	3. Refrigerant flow through the A/C evaporator is restricted.	3. See A/C EVAPORATOR . Replace the restricted A/C evaporator, if required.
	4. Faulty A/C compressor.	4. See A/C COMPRESSOR . Replace the A/C compressor, if required.
The low side pressure is normal or slightly high, and the high side pressure is too high.	1. A/C condenser air flow restricted.	1. Check the A/C condenser for damaged fins, foreign objects obstructing air flow through the condenser fins, and missing or improperly installed air seals. Clean, repair, or replace components as required.
	2. Inoperative radiator cooling fan.	2. Test the radiator cooling fan and replace, if required.
	3. Refrigerant system overcharged.	3. See STANDARD PROCEDURE - REFRIGERANT SYSTEM CHARG . Recover the refrigerant from the refrigerant system. Charge the refrigerant system to the proper level, if required.
	4. Air in the refrigerant system.	4. See DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS . Test the refrigerant system for leaks. Repair, evacuate and charge the refrigerant system, if required.
	5. Engine overheating.	5. Test the engine cooling system and repair, if required. Refer to COOLING .
	6. Faulty A/C orifice tube.	6. See A/C ORIFICE TUBE . Replace the liquid line if required.
The low side pressure is too high, and the high side pressure is too low.	1. Accessory drive belt slipping.	1. Inspect the accessory drive belt condition and tension. Tighten or replace the accessory drive belt, if required. Refer to ACCESSORY DRIVE .
	2. Faulty A/C orifice tube.	2. See A/C ORIFICE TUBE . Replace the liquid line if required.
	3. Faulty A/C compressor.	3. See A/C COMPRESSOR . Replace the A/C compressor, if required.
The low side pressure is too low, and the high side pressure is too high.	1. Restricted refrigerant flow through the refrigerant lines.	1. See PLUMBING . Inspect the refrigerant lines for kinks, tight bends or improper routing. Correct the routing or replace the refrigerant line, if required.
	2. Restricted refrigerant flow through the A/C orifice tube.	2. See A/C ORIFICE TUBE . Replace the liquid line, if required.
	3. Restricted refrigerant flow through the A/C condenser.	3. See A/C CONDENSER . Replace the restricted A/C condenser, if required.