Originally Posted by Bud
There should be another schematic showing compresor and condensor unit. Next time it does not start check voltage at compressor. then work back to source. Should go through an overload protect, relay. a high pressure switch and sometimes a low pressure switch. As you check voltages you can inspect for loose connections.
It's a Danfoss compressor with SECOP module. Conventional compressor troubleshooting doesn't apply.
The 1st step in DX the module would be installing an LED between (+) and "D". It will give you an error code if the module is tripping. Instructions along with error code keys are easy to find on SECOP's website, and myriad other sources on the web. These modules are very intolerant of low voltage, so check the voltage with a DMM at the (+) / (-) terminals on the module while the unit is operating
. Checking static voltage is not conclusive. Anything under 12.0 VDC can create a problem. Power wiring should be liberally sized, you can't go too big, too small is typical. Size for minimal voltage drop ~1%.
A flakey thermostat that chatters can easily make the compressor start/stop/start, this will create an error condition.
The LED will tell you why it's shutting down. Modules run around $300, depending, and they are not particularly robust. Older vintage were sensitive to temperature problems, they would cook themselves. The hammer DX was more likely a fluke.