Heat pump not heating, or blowing cool air

Question 1: What is the thermostat set to?

• Heat, fan on Auto, set above room temperature: go to question 2
• Cool, or the fan set to On: Likely cause: a thermostat setting

Question 2: Go look at the outdoor unit. What is it doing?

In defrost, the outdoor fan stops for a while, you may see steam, and the air inside runs cool briefly.

• The fan is stopped, there's steam, or light frost is melting: Probably normal: defrost mode
• It's buried in snow, leaves or debris: Likely cause: a blocked outdoor unit
• It's encased in thick ice that isn't clearing: Likely cause: refrigerant, a reversing valve or an electrical fault
• It isn't running at all: go to question 3
• It's running normally: go to question 4

Question 3: Check the breakers, the outdoor disconnect and the indoor unit's switch. What do you find?

Open only the hinged panel door, never the metal cover behind it. Reset a tripped breaker only once. Carrier notes the outdoor unit has its own 220 or 240 volt breaker. The disconnect is a small box on the wall near the outdoor unit.

• Something was off or tripped, and it held after one reset: Likely cause: a switch or breaker was off
• A breaker tripped again after one reset: Likely cause: refrigerant, a reversing valve or an electrical fault
• Everything was already on: Likely cause: refrigerant, a reversing valve or an electrical fault

Question 4: How does the air filter look?

Slide the filter out and hold it up to a light.

• Gray or dusty, and little light comes through: Likely cause: a clogged air filter
• Clean, or changed in the last month: go to question 5

Question 5: Which of these fits best?

• A hissing sound, or oily residue or liquid pooling near the unit: Likely cause: refrigerant, a reversing valve or an electrical fault
• It's very cold outside and the air is only mildly warm: Probably normal: deep cold reduces output
• None of these: Likely cause: refrigerant, a reversing valve or an electrical fault