Trouble Shooting and Performance Testing CHAPTER Trouble Shooting and Performance Testing 10 Instructor Name: (Your Name)

Learning Objectives Identify proper safety equipment worn when servicing HVACR systems. Explain how to work safely on pressurized HVACR systems. List rules that should be followed whenever a system has been opened to atmosphere. Explain how to performance test an HVACR system.

Learning Objectives (continued) Identify a system that contains some air and moisture. Identify a system that has excessive air and moisture. Identify a system that has restricted air flow through the condenser or is overcharged. Identify a system that has a low refrigerant charge.

Learning Objectives (continued) Identify a system that has a very low refrigerant charge. Identify a system that is overcharged with refrigerant. Identify a system that has a restriction in the high pressure side of system. Identify a system that has a TXV that will not open.

Learning Objectives (continued) Identify a system that has a TXV held open. Identify a system that has a defective thermostat switch. Identify a system that has a defective compressor. Identify the difference between purging and flushing an A/C system. List the procedures for purging an A/C system.

Learning Objectives (continued) Explain the procedures for flushing an A/C sys. Explain how to pop dry a system after a full flush has been performed.

CAUTION Air conditioning systems are always under pressure. Before internal system repairs are made refrigerant must be recovered from system. Once repairs are complete the system must be evacuated and recharged before it can be returned to service.

Air Conditioning Safety Safety glasses Non leather gloves Proper ventilation Refrigerant must be stored below 125 degrees Fahrenheit Refrigerant oil must be stored in air tight containers Do not mix refrigerant oils

Servicing When system is open cap disconnected lines. Replace and lubricate all o-rings on disconnected lines. Replace receiver dryer or accumulator on opened system. Keep manifold gauge set connected when servicing. Replace all lost refrigerant oil.

Servicing (continued) Prior to any service work is performed, talk to drive to obtain any problematic history of the unit. Questions should include; Did the A/C fail all at once or gradually loose its effectiveness? Does the A/C work occasionally or not at all? Has the A/C been worked on or serviced recently?

Performance Testing Run engine at 1500 rpm, close all windows Run A/C on max for minimum 10 minutes to stabilize system. Insert thermometer in air vent, let system stabilize Check for proper vent and fan operation. Visually inspect compressor, compressor clutch, and drive belt. Feel the suction and discharge lines at compressor. Suction line should be cold and discharge line should be hot.

Performance Testing Cont. Feel condenser inlet and outlet line there should be a large change in temperature. Feel condenser to receiver dryer line, feel for warm or cold spots. Feel inlet and outlet of receiver dryer, they should be the same temperature. Feel outlet of receiver dryer to TXV line, it should be a consistent temperature.

Performance Testing Cont. Feel the suction line from evaporator to compressor, it should be cold. If engine is running hot or heater water valve is stuck open the system will not cool. Check discharge air temperature. It will vary according to ambient temp and humidity. Shut down unit. Feel condenser for cold spots indicating restrictions.

Troubleshooting Flow Chart

Manifold Gauge Set Connection

Pressure Temperature Chart

Gauge Reading, Some Air and Moisture in System

Gauge Reading, Some Air and Moisture in System Symptoms Not cooling effectively Moisture indicator show moisture level high in system Low pressure cycling does not respond to the on/off cycle of thermostatic switch Cause Air or moisture in system. Probably caused by external leak in low side of the system. Cure Leak test the system Remove refrigerant, repair any leaks found

Gauge Reading, Some Air and Moisture in System (continued) Cure (continued) Flush and purge system if required Top up oil if required Replace the receiver dryer Evacuate the system Charger with recommended weigh of refrigerant

Gauge Reading, Excessive Air and Moisture in System

Gauge Reading, Excessive Air and Moisture in System Symptoms Not cooling effectively Moisture indicator show moisture level high in system Suction pressure is high in the beginning but as system operates may drop to low or even vacuum Discharge pressure is high Cause Receiver dryer saturated allowing moisture to freeze at the TXV High pressure caused by excess air in system

Gauge Reading, Excessive Air and Moisture in System (continued) Cure Leak test the system Reclaim refrigerant, repair any leaks Flush and purge as required Top up refrigerant oil Replace receiver dryer Evacuate system Charge with recommended weight of refrigerant

Gauge Reading, Obstructed Condenser or Over Charged System

Gauge Reading, Obstructed Condenser or Over Charged System Symptom Not cooling effectively Suction line warm Discharge line too hot Truck engine may be overheating High pressure relief open opening circuit to clutch Cause Fan belt slipping, clutch fan faulty Refrigerant is excessively overcharged

Gauge Reading, Obstructed Condenser or Over Charged System (continued) Cure Clean condenser and radiator, do not use a pressure washer Check condition and tension of fan belt. Check fan speed and replace clutch fan if necessary Recover refrigerant. Top up oil if necessary. Charge with recommended weight of refrigerant. Test system pressure. If still high test for restriction in high side.

Gauge Reading, Low Refrigerant Charge

Gauge Reading, Low Refrigerant Charge Symptoms Not cooling effectively Slightly lower than normal suction and discharge pressure Cause A very small leak in the A/C system Cure Leak test the system Repair any leaks found Flush and purge system if required

Gauge Reading, Low Refrigerant Charge(continued) Cure Top of oil if required Replace receiver dryer Evacuate the system Charge with recommended weight of refrigerant

Gauge Reading, Very Low Refrigerant Charge

Gauge Reading, Very Low Refrigerant Charge Symptoms Not cooling Discharge air from evaporator may be warm Compressor not running or cycling frequently Low pressure switch consistently open Cause Leak in air conditioning system Cure Leak test the A/C system

Gauge Reading, Very Low Refrigerant Charge (continued) Cure (continued) Recover refrigerant and repair any leaks Flush and purge system if needed Remove refrigerant and flush of required Top off oil if required Replace receiver dryer Evacuate system Charge with recommended weight of refrigerant

Gauge Reading, Restriction in High Side of System

Gauge Reading, Restriction in High Side of System Symptom Not cooling effectively Frosted discharger line beyond restriction If restriction is between compressor and inlet of receiver, discharge pressure may be excessively high High pressure switch is open Cause Restriction between compressor discharge and inlet of TXV

Gauge Reading, Restriction in High Side of System (continued) Cure Feel discharge line for cold spots to identify the point of restriction Recover refrigerant and flush of required Replace defective component if it can’t be flushed Top up oil if required Replace receiver dryer Evacuate system Charge with recommended weight of refrigerant

Gauge Reading, TXV Not Opening Enough

Gauge Reading, TXV Not Opening Enough Symptoms Not cooling effectively Sweat or frost build up on expansion valve Suction or discharge pressure return to normal if heat is applied to TXV Cause The TXV does not open enough The TXV is stuck closed Problem with capillary tube or sensing bulb Blockage at the orifice tube in CCOT system

Gauge Reading, TXV Not Opening Enough (continued) Cure Repair TXV if possible, if not go to Step 2 Recover refrigerant and flush system if required Replace TXV, do not damage or crimp capillary tube Top up refrigerant oil Replace receiver dryer or accumulator Evacuate system Charge with recommended weight of refrigerant

Gauge Reading, TXV Held Open

Gauge Reading, TXV Held Open Symptom Not cooling effectively, cools well in beginning but evaporator freezes over and blocks air flow Sweat or frost build up on TXV Suction valve sweats heavily System pressure returns to normal if evaporator is allowed to defrost Cause The TXV stuck open flooding evaporator Problem with sensing bulb or capillary tube

Gauge Reading, TXV Held Open (continued) Cure Repair TXV if possible, if not go to Step 2 Recover refrigerant and flush if necessary Replace TXV, be careful to not damage or crimp capillary tube Top up oil if necessary Replace receiver dryer Evacuate the system Charge with recommended weight of refrigerant

Gauge Reading, Defective Thermostatic Switch

Gauge Reading, Defective Thermostatic Switch Symptoms Not cooling effectively. Compressor runs constantly and may become noisy Evaporator freezes up, blocking air flow Cause Defective thermostatic switch not disengaging clutch at temp below 32 degree f Bent, kinked, or broken capillary tube causing thermostatic switch to malfunction

Gauge Reading, Defective Thermostatic Switch (continued) Cure Inspect condition of capillary tube for thermostatic switch. Perform electrical test on the switch Rectify any problems found with capillary tube If capillary tube can’t be corrected, replace thermostatic switch

Gauge Reading, Defective Compressor

Gauge Reading, Defective Compressor Symptoms Not cooling effectively Noisy compressor operation with no compressor cycling Cause Compressor drive belt loose or worn Compressor clutch not operating Internal compressor failure Defective trinary or low pressure switch Cure Inspect/replace compressor drive belt Inspect/replace engine drive pulley

Gauge Reading, Defective Compressor (continued) Cure (continued) Inspect/replace compressor clutch Test trinary switch electrically, replace if necessary If compressor is replaced, flush system Top off oil if necessary Replace receiver dryer Evacuate system Charge with recommended weight of refrigerant

Flushing and Purging Purging blows out wet air, refrigerant, and loose dirt from system Flushing is used to clean extremely contaminated systems. Purging, use dry nitrogen. HCFC 141b. Is commonly approved by system manufacturers Some manufactures do not endorse flushing and are not covered under their warranty.

Summary A/C systems are constantly under pressure. Always wear appropriate PPE when working on a charged A/C system R-134a can be combustible under the right conditions. A/C system should never be pressure or leak tested with compressed air, a fire or explosion could result.

Summary cont. PAG oil containers should always be kept tightly closed. When a system is open, always cap disconnected lines. Whenever A/C lines are disconnected always replace and lubricate o-rings. Receiver driers must be replaced when a system is opened. Manifold gauge fittings should be connected to manifold when not in use.

Summary cont. Add refrigerant oil to replace any that may have been lost. Always question operator about problems and history of problems. Performance tests identify problems that may exist. To check levels of R-134a, a performance test with gauge set must conducted. If refrigerant is low, repair leaks, recover all coolant and refill. DO NOT TOP OFF SYSTEM.

Summary cont. Use dry nitrogen to purge wet air and loose dirt from and A/C system. Use liquid flushing agents to clean contaminants from A/C components. Popping components dry is a process of drying A/C components with quick shots of dry nitrogen.