scroll compressor running but not pumping

It is highly encouraged that the mechanic recover refrigerant in order to lower the pressure in the system. Remember, always keep to one side of the unit when working on single-phase compressors! Not only can that damage the unit, but it can send the terminal through anything that is in front of it – be that your hand or any other body part.

Therefore, when you remove the compressor leads (wires) from the plug to check resistance through the compressor windings, the pressure of the Freon can launch the plugs with as much as 20,000 pounds of force.

Remember to exercise extreme caution because on a 90-degree day, the pressure in a de-energized R410A system can be approximately 275 psi and when a compressor has shorted out, the plug can overheat and become soft. In the case that any of the tests above fail, you need to check the compressor posts themselves. Allowing the compressor to cool down should reset the internal overload but you need to investigate further ensure the reset was indeed completed. In this case, the compressor may be extremely hot to the touch. If it’s tripped, you will read infinity (OL) between S to C and R to C, while seeing a measurable resistance between R to S. The internal overload is wired in series with both the start and run winding which prevents the compressor from coming on. This can be due to excessive loads, poor airflow or lack of superheat. Remember, there should be a measurable resistance through each winding.Ĭompressors are equipped with internal overload devices which open on a rise in temperature. Finally, the resistance between run and start should be the sum of S to C and R to C. The resistance between start(S) to common(C) is typically three-to-five times higher than run to common winding. The lowest resistance will be found between the run(R) to common(C). There should be a measurable resistance through each set of wires. With the multimeter set to R x 1 scale (ohms), measure the resistance between the run and start wires start and common wires and run to common wires. Once the wires are disconnected, you can ohm out the wires, plug and compressor as they all require an inspection. Next, locate the three wires that power up the compressor – the common, start and run winding – and remove the wires from the contactor and the capacitor. We’re dealing with electricity here don’t mess around!įor safety’s sake, the first thing you need to do is disconnect the power at the unit disconnect or breaker. Approximately one in 20 HVAC technicians suffer injuries that could be prevented by taking the proper safety precautions. Have you ever faced the situation where you have a brown plug and need a safe way to measure ohms on a single-phase compressor?īefore you begin any work, ensure your work space is safe. In this 6-minute video, Doug Smiley, Technical Training Manager, shows how to read ohms on a compressor.

Scroll compressor running but not pumping