Tech arrived to no heat call for basement system. System is approximately 2/3 years heat pump system servicing downstairs. On arrival found low voltage blown. Checked all thermostat wiring inside and out, and found no signs for direct shorts or any wires touching metal or ground. Replaced fuse and watched operations. System did not replicate scenario after replacing fuse. Found outdoor temperature sensor partially pinched in fan area, moved to chase where wiring is designated. Contacter is within specs at this time. Notified partial discoloring at thermostat. System does not have water protection safeties up to TE’s standards. Verified heat strips are operational. Brought recommendations to customer. Customer agreed to sign up for HomeCare on two systems in home. Tech replaced customer provided customers thermostat. No warranty on thermostat outside of warranty. Flood protection waiver noted. Replaced 16x20x1 filter for basement and replaced customer supplied 20x20x1 upstairs. Thank