The capacitor and potential relay can be checked in the field without the need of diagnostic equipment.
If a single phase compressor will not start, then "jump start" it!
What's that? You've never jump started a compressor?
It's a simple procedure.
Turn off the compressor.
Before working on any refrigeration component using caps, I always start here.
Next, disconnect all the wires from the potential relay and start cap.
Rig up a new start cap (same rating and size) with a single wire attached to each set of terminals.
Strip the insulation off the ends of the wires.
While touching one wire to one terminal and the other wire to the other terminal of the run cap, turn on the compressor.
Quickly pull these wires off the run cap.
If the compressor starts and run normally, chances are you have a bad potential relay and/or start cap.
Want to narrow it down even more?
Repeat the above using the old start cap. If it starts the compressor, the old cap is OK.
It's probably a bad potential relay.
The above procedure simply mimics the action of the potential relay.
The relay does the same thing. The start cap is momentarily applied to the circuit, then quickly disengaged.
I've used this procedure many times.
Remember, short out the start cap used above. All you have to do is touch the ends of the wires together.
What if the compressor still doesn't start?
Here's some additional information that may help.
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