Identifying Compressor Terminals: Start, Run, and Main

Compressor Power TerminalsLet’s say you’re gonna do some tests on your refrigerator compressor to see if it’s okay. Or, you need to figure out how to wire up a generic (Supco) start relay/overload combination. So you pull the relay cover off the compressor, remove the relay/overload and this is what you see.

You need to figure out which posts correspond to the Start, Main, and Run windings ‘cuz if’n you don’t and you go and wire that relay/overload up wrong, well, you just went from a $30 easy-as-pie repair to a $300 rectal cramp.

What’s a brutha to do?

Well, urine luck, budrow, ‘cuz one of the wise and beneficent Sublime Masters of Appliantology at the Samurai Appliance Repair Forums, Bobice, has graciously prepared this little primer on how to tell them little posts apart. Let’s give a listen to Master Bob:

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 (C)

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”

Kin Ah hears a “Amen?”

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