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Heat pump outside unit not running: normal pause or fault?

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An outdoor unit that sits still is not always broken. Some pauses are by design, and some are a warning to leave alone.

If your heat pump's outside unit is not running, do not assume the worst. The outdoor unit pauses on purpose in several situations. Others point to a real fault.

Sort out which one you have before you call anyone.

Is the system actually calling for heat?

Set the thermostat to heat, a few degrees above the room temperature. If the setpoint is already met, the outdoor unit has nothing to do. Check that the mode is heat and not off or cool, and replace the batteries if the thermostat takes them.

Defrost and restart delays are normal

In cold, damp weather the unit runs a defrost cycle, and the outdoor fan often stops for a few minutes while it does. After a power blip, the compressor also waits several minutes before it restarts. Give it at least five minutes before you decide anything is broken.

Check the indoor side too

If the indoor blower is running but the outdoor unit stays silent, the signal or the power to the outdoor half is the likely issue. If both are dead, the thermostat or the main breaker is more likely. Each points you to a different next step.

Look at the breaker and the outdoor disconnect

Check the breaker for the outdoor unit and the disconnect box mounted near it. Either can trip or be switched off. Reset a tripped breaker once. If it trips again, stop there. A repeat trip means a fault, and forcing it can cause damage.

Look, but do not dig

From a few feet away, check for heavy ice, packed snow or debris around the cabinet. Clear loose leaves and snow by hand. Do not chip at ice with tools, since the coil fins damage easily. A unit that stays buried in ice and never clears needs a technician.

What not to do

  • Do not take off the outdoor unit's panels or touch the wiring or capacitor inside. A capacitor can hold a dangerous charge even when the power is off.
  • Do not try to add or check refrigerant. Federal law requires EPA Section 608 certification, and it is illegal without it.
  • Do not keep resetting a tripping breaker.

When to call a licensed HVAC technician

Call one if the unit stays silent after the delay, the thermostat and the breakers all check out. Or you hear a hum from the unit with the fan still. The cause is then inside the cabinet, and that is electrical and refrigerant work for a licensed professional.

Frequently asked questions

Is it normal for a heat pump's outdoor unit to stop running?

Yes, in some cases. It pauses during defrost cycles and waits a few minutes before restarting after a power interruption, and it idles when the thermostat is satisfied.

Why is the indoor unit running but the outside unit is not?

The outdoor half may be on a delay, its breaker or disconnect may be off, or it may have locked out. Wait five minutes, then check the breaker and disconnect.

Can I open the outdoor unit to see what is wrong?

No. Parts inside can hold a dangerous electrical charge even when the power is off. Leave the cabinet closed and call a licensed HVAC technician.

Sources

What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.

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