In this article, we explain how to diagnose and resolve issues when the current draw of an air conditioner compressor exceeds normal values. Using a clamp meter, you can easily measure the amperage while the equipment is operating and compare it to the values indicated on the manufacturer’s label.
The key parameters to monitor are the RLA (Rated Load Amperage) during normal operation and the LRA (Locked Rotor Amperage) when starting the unit. If you find the current draw exceeds these values, follow the steps outlined below.
1. Clean the Condenser or Outdoor Unit
If the measured amperage is above the RLA but the unit is still running:
- Clean the outdoor unit with water and soap to remove dirt that may obstruct heat exchange.
- Ensure the condenser fins are not bent or blocked.
2. Check the Airflow
Low airflow in the condenser can cause overheating and increase the amperage.
- Inspect the outdoor unit fan.
- If the fan is not operating correctly, test another capacitor to confirm whether the original is faulty.
3. Inspect the Compressor Capacitor
If the amperage remains high, check the compressor capacitor:
- Replace it with one of the same technical specifications.
- Verify if the problem persists.
- Inspect electrical connections, including terminals and contacts. Look for hot spots that may indicate issues.
4. Measure the Supplied Voltage
Low voltage can lead to increased compressor amperage.
- Measure the voltage received by the unit.
- Ensure it falls within the range recommended by the manufacturer.
5. Test the Compressor Coil Resistance
With the equipment turned off:
- Measure the resistance of each compressor coil.
- Check for any current leaks to the ground.
- If you have a service manual, compare the measured values. If not, remember that the sum of the resistances between the run-common and start-common pins should equal the resistance between the start and run pins.
6. Check the Refrigerant Charge
Excess refrigerant can increase pressure and amperage.
- Ensure no unnecessary refrigerant has been added, particularly if a capillary blockage was mistakenly identified as a leak.
- Adjust the refrigerant charge to the specified level.
7. Troubleshoot Starting Issues
If the measured amperage does not exceed the LRA but the unit struggles to start:
- Install a start-assist kit. This can prolong the compressor’s lifespan.
8. When the Amperage Exceeds the LRA
If the current draw surpasses the LRA, this indicates a serious problem, either mechanical or electrical.
- In most cases, replacing the compressor is necessary to resolve the issue permanently.
