1: Did I damage my heat pump? 2: Should I simply replace the defrost sensor & circuit board?

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Dec 11, 2022
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During a particularly cold night, my 12-year-old Carrier heat pump (Model 25HBC336W0030010) coils froze up solid.

The next day, which was remarkably warmer than the night before…

  • A repair tech checked the refrigerant level with a simple set of pressure gauges and said the refrigerant level was fine.
  • The tech ran the heat pump for about 45 minutes without tripping the defrost sensor.
  • When his assistant asked if it was too warm to trip the defrost sensor, the tech said, “Probably, but clearly the defrost sensor or circuit board are bad and both should be replaced.”
  • The tech did not confirm his suspicion with either a resistivity or ice cube/screwdriver test.
  • The tech removed the pullout disconnect, but said we could use EMERGENCY HEAT if needed, which we did seven or eight times.

Question 1: Did we damaged the heat pump using EMERGENCY HEAT with the pullout disconnect removed?

Question 2: Did running the heat pump on COOL last night for six hours with the pullout disconnect removed damage the unit?

Question 3: Should I simply replace (DIY) the defrost sensor and circuit board without any additional testing?

Question 4: Can I run the heat pump to cool the house for a few hours each night while waiting for the parts to come in and if so, should I reinstall the pullout disconnect first?

Thank you so very much for all assistance!

If it's something you can do yourself for not a lot of money for testing purposes I'd say that's the thing to do, especially considering you wouldn't want to replace the entire system.

Hopefully things will work out and you'll get another 12 years of service.