Compressor-Testing The Easy Way!

Compressor-testing is necessary when your refrigerator or freezer keeps on running, but the stuffs inside are becoming spoiled. We suspect that there is something wrong with the compressor.

There are two ways of testing your compressor. One is through electrical testing, and the other is through mechanical testing.

I find both are necessary to justify a purchase for a new compressor. For this demonstration, we are going to test a compressor of a refrigerator. or a freezer.

Electrical Compressor Testing:

1) On the side of the compressor you will find a round bake-e-lite

with three pins on it. They are always in a triangular configuration.

The three terminals are C (common), S (Start), and R (Run). The top pin is the “C”, the one on the left is “S”, and the one on the right is “R”.

2.) Now get the ohmmeter ready, adjust the selector to x1; touch the test prods and adjust to “0”. Write down on a piece of paper like the one below:

1 – 2 = ________ ohms

1 – 3 = ________ ohms

2 – 3 = ________ ohms

1 = C, 2 = S, 3 = R

3) Get the resistance reading of 1 and 2; followed by 1 and 3; and finally 2 and 3. Fill in their reading on the paper. Normally the 1 and 2 resistance should be around 15 ohms, 3 ohms for 1 and 3, and 18 ohms for 2 and 3.

4) If either one has no reading, it means that there is an open circuit inside the winding. And if the reading is too high, there could be a short circuit in it. Check the pins to the ground for short. It should not exhibit any form of continuity.

Mechanical compressor-testing:

1) Now, we will test the compressor for internal problems; like loose compression or leaky valves.

2) While still connected in the system, connect a compound gauge on the service valve of the suction copper coil; and a pressure gauge on the service valve of the discharge copper coil. Check for refrigerant leaks.

3) Turn on the compressor and observe the reading. If the reading is the same, for example: both are 35 psig, you have a loose compression.

4) Now remove the compressor from the system, and connect a compound gauge on the suction side, and a pressure gauge on the discharge side.

5) Run the compressor and observe the reading. When the reading of the compound gauge is around 25 psig, and the reading of the pressure gauge is around 135 psig.

Turn off the unit and observe the reading of the needles. If both needle fall after 15 minutes, then your valves are leaking.

Compressor-testing may not be so hard, just follow the tips above, and with a little common sense, and some knowledge on refrigeration, you should be on the right track.

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