I'm having issues with my Air Condenser outside, the fan turns on and stays on; however, the compressor kicks on, but only stays on for seconds and powers back off, then a about 20 seconds later, it tries to kick back on, only to kick back off, this continues to happen until I turn the unit off at the thermostat. Any suggestions on where to begin? The unit was working fine last night, started happening overnight I suppose (We did have a hard freeze in the area last night, and heater was running heavy all night). It's a Lennox 13HPD Condenser. Thanks in advance for your help.