How to Check for Resistance Between Windings in Compressors

In any electric refrigeration system, the compressor is responsible for reducing the volume of a coolant gas until it reaches the expander valve, which allows the gas's temperature to plunge by way of adiabatic expansion.
When the compressor malfunctions, the gas doesn't compress and its temperature doesn't plunge when it reaches the expander valve. Electrical power from the building is converted into mechanical power that compresses the gas thanks to a set of coiled wires known as armatures or "windings". If a compressor is experiencing difficulty starting, there may be a continuity problem with the windings.

Step 1

Turn the appliance off and unplug it from the electrical outlet.

Step 2

Remove the screws securing its housing with the screwdriver.

Step 3

Remove the housing.

Step 4

Remove the starting relay from the compressor's three-pronged electrical terminal. The windings run between these three prongs.

Step 5

Turn on the multimeter and set its detection mode to "Ohms." Signified by the Greek symbol "Omega", ohms are the standard measurement unit for electrical resistance.

Step 6

Touch the metal tip of the black multimeter probe to the first terminal and the metal tip of the red probe to the second terminal.

Step 7

Write down the resistance (in ohms) displayed by the multimeter. Label this value "Resistance 1-2."

Step 8

Touch the metal tip of the black multimeter probe to the second terminal and the metal tip of the red probe to the third terminal.

Step 9

Write down the resistance (in ohms) displayed by the multimeter. Label this value "Resistance 2-3."

Step 10

Touch the metal tip of the black multimeter probe to the third terminal and the metal tip of the red probe to the first terminal.

Step 11

Write down the resistance (in ohms) displayed by the multimeter. Label this value "Resistance 3-1."

Step 12

Rank these resistances in order, from smallest to largest.

Step 13

Add the smallest and second largest numbers together. The sum of these two resistances should equal the valve of the largest. For example, if the resistances of the first two windings were 3 ohms and 5 ohms, the value of the third winding should be 8 ohms (i.e. 3 + 5 = 8). If these resistances don't add up to the third, it could be the sign of a short circuit somewhere within the windings. Note: if the multimeter displays "infinity" for the resistance between two terminals, it means that the compressor's internal overload protection feature was triggered during use.

Things You Will Need

  • Screwdriver
  • Multimeter
  • Pen
  • Paper

About the Author

A Chicago-based copywriter, Andy Pasquesi has extensive experience writing for automotive (BMW, MINI Cooper, Harley-Davidson), financial services (Ivy Funds, William Blair, T. Rowe Price, CME Group), healthcare (Abbott) and consumer goods (Sony, Motorola, Knoll) clients. He holds a Bachelor of Arts in English from Harvard University but does not care for the Oxford comma.