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Rigging and using a compressor test cord to manually operate a compressor

Posted by Samurai Appliance Repair Man, in Refrigerator Repair 21 June 2013 · 2,949 views

compressor refrigerator test cord
One of the many things that can make a refrigerator warm up is the compressor is trying but failing to start. You may occasionally hear this type of noise from the back of the refrigerator (starts about 15 seconds in):

This is the sound of your compressor trying, but failing miserably, to start. Best case scenario: Bad compressor start relay. Worst case scenario: open compressor start winding or seized compressor bearing == buy a new refrigerator.

Question: How do you tell which is which?

Answer: Compressor test cord.

Question: What's a compressor test cord and how do I make one?


Posted Image

Question: How do you know which is the start, run, and common connection posts on the compressor?

Answer: Use Brother Bobice's procedure for identifying the compressor electrical terminals:

Using a good multimeter set on ohms, remove the compressor terminal cover with the unit off.

Touch one lead (of the meter) to one terminal and the other lead (of the meter) to one other terminal and record your reading . Lets call these terminals (A) and (B). The remaining terminal lets call ©

So for example A-B=7 Ohms

Now lets read A-C and record. Lets say 5 Ohms

Now lets read C-B and record. Lets say 12 Ohms

Now lets add all the A’s= 12 Ohms

Now lets add all the B’s=19 Ohms

Now lets add all the C’s=17 Ohms

The highest reading will be the “Start” winding

The next highest reading will be the “Run” winding

The lowest reading will be the “Common” winding

Therefore B= “Start”

The next is C=”Run”

The remaining terminal A= “Common”

Just a reminder: Never ever introduce 120v directly to an inverter compressor. Ie if you don't see a start relay, don't use a test cord.
I have a direct devise i got from G.E 30 years ago make by ROBINAIR that iforgot to give back to them 30 YEARS ago and its made just like your diagram.Comes very handy.

I made one several years ago and it has really helped me. Looks like I won't be using it much in the future though.

Why in the described testing procedure in steps 3 and 4 your resistance R to C equals S to C. Shouldn't S to C be much higher then R to C?

Could you please be more specific about what you're referring to as steps 3 and 4?


I actually teach a much simpler method in the Refrigerators course. Stick with the method taught there.

A couple of questions on the compressor cord. Should The circuit breaker fuse be 15 A? And is it on the neutral wire ? How many Mississippi's do I count on a momentary switch?

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