Isaac J. Came out to call for a system not heating properly and the customers thermostat was blank. Checked system over and found a blown low voltage fuse. Went through the system low voltage wiring and found no issues initially. Outside thermostat wiring was close to the condenser coil and maybe water from the unit defrosting got into the wire nuts and caused the short. I’m not 100% for sure if that’s the issue though. Left unit on emergency heat for customer and let him know that we’ll come back to double check the operation of the heat pump when temperatures get above freezing. Isaac J. System has an intermittent low voltage short that I was not able to locate. Put a resetable fuse in just in case. Might have to do with the heat pump condenser, but it is too cold to try and run diagnostics on it at the moment. Need to reschedule for next week. Emergency heat is operating and customer is aware to leave it on that until we can figure out the problem. Jake K. I arrived to track down