13-Troubleshooting Steps For No CoolingChecking AC

Step-5: Does the outdoor fan run?

If the outdoor fan runs, you at least know that the outdoor unit has line voltage power.

If the outdoor fan doesn't run, start by measuring the power supply to the outdoor unit. If there is no power, check the breaker, fuses, or disconnect. 

If there is power to the outdoor unit, but the outdoor fan is not running, check to see if the contactor is pulled in. If it is pulled in, check for power to the outdoor fan motor leads. If there is no power at the outdoor fan motor leads, check the wiring for breaks. If there is power at the outdoor fan motor leads, check the run capacitor. If the run capacitor is faulty (open, shorted, weak), replace it with a properly rated capacitor. If the run capacitor is fine, check the outdoor fan motor for continuity; replace if it measures "open".

If the contactor is not pulled in, check to see of the contactor coil is being energized with 24-volts. If the contactor coil is not energized, jumper R-to-Y at the indoor unit. If the contactor coil still isn't energized, you most likely have an open low voltage control wire or faulty connection between the indoor & outdoor units. If the contactor coil energizes, you potentially have a faulty thermostat or control wire between the thermostat and indoor unit.

If the contactor is being energized but not pulling in, check the coil for continuity; replace if it measures "open".

Step-6: Is The Condenser Airflow Clear?

If the airflow is clear, and appears to be blowing "strong", proceed to the compressor unit at this time.

If the airflow seems "weak" or "not-so-strong", make a visual inspection of the airside components. Is the coil clean? Are there recirculation issues? Is the clearance adequate around all sides of the unit? Are there bushes, shrubs, landscaping, etc restricting airflow? Is the fan blade correct? Is the blade in the correct position on the shaft & in the opening? Is there fin damage to the coil? Is the motor rotation correct? Is the run capacitor within +/-5% of rated capacity?

If you answer "yes" to any of these potential issues, make the necessary corrections.

Step-7: Does The Compressor Run?

If the compressor runs, proceed to checking the charge.

If the compressor doesn't run, check for power to the compressor motor leads. If there is no power at the compressor leads, check the wiring for breaks. If there is power at the compressor motor leads, check the run capacitor. If the run capacitor is faulty (open, shorted, weak), replace it with a properly rated capacitor. If the run capacitor is fine, check the compressor motor for continuity; if it measures "open" touch the compressor to see if it's hot; if hot, let it cool down, then retest continuity. If it continues to measure "open", replace the compressor.

Step-8: Check System Charge

Purge & attach gauges to hi-side and lo-side.

Attach temperature sensors to liquid and suction lines to measure subcooling and superheat. 

Measure return air DB/WB temperatures entering indoor unit.

Measure outdoor air temperature entering outdoor unit.

Based on type of metering device, compare readings to charging chart and/or specifications.

NOTE: Evaporator and Condenser airflow must be correct before being able to accurately check charge!

Steps 9-13 Are Covered Separately.

 


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