Rheem Heat Pump Runs Constantly: Causes, Fixes & Costs

Last updated Oct 18, 2026 · By fixme.vip Editorial

Rheem heat pump runs constantly: what it means

“Runs constantly” is not a numbered Rheem fault code. It describes a heat pump that never reaches setpoint and cycles off, or that keeps running after the thermostat stops calling. Because the control board usually doesn’t see a fault, there is typically no flashing code, no lockout, and nothing to reset.

The first question is whether the long run time is a problem at all:

• Normal behavior in cold weather. Below the system’s “balance point,” usually around 25–35 °F, a heat pump may run nonstop in heating mode.
• Normal for two-stage and variable-speed models. Two-stage and variable-speed Rheem Prestige units are designed for long, low-speed runs.
• A real problem. It’s a fault when the unit runs nonstop in mild weather or in cooling mode, when the house falls short of setpoint, or when the outdoor unit keeps running with the thermostat off.

This page covers the heat pump itself. If backup electric heat is the part that never shuts off, see the Auxiliary Heat On Constantly page.

Rheem heat pump runs constantly: common causes, ranked by probability

1. Operating below the balance point (not a fault). In cold weather the heat pump’s output falls until it can no longer keep up with heat loss, so it runs continuously with auxiliary heat assisting.
2. Thermostat setting or placement. Common culprits include:
   • Fan set to ON instead of AUTO, which keeps the blower running.
   • An unrealistic setpoint.
   • Wrong mode.
   • A thermostat near a drafty door, a supply register, or sunlight.
   • A thermostat not configured for heat-pump operation.
3. Restricted airflow. A clogged filter, closed or blocked registers, or a dirty indoor coil cuts capacity, so the system can’t satisfy the call.
4. Dirty or obstructed outdoor coil. Debris, cottonwood, leaves, or snow around the outdoor unit reduce heat transfer in both modes.
5. Low refrigerant charge from a leak. This reduces capacity and lengthens cycles. It often comes with icing or weak air temperature.
6. Welded or stuck contactor. The outdoor unit keeps running even when the thermostat is satisfied or turned off. This is a classic cause of truly nonstop operation.
7. Control-wiring or thermostat fault. A shorted thermostat wire or a failed thermostat holds the call on.
8. Reversing valve leaking through or stuck partway. Hot and cold refrigerant mix internally, so capacity drops sharply in one or both modes.
9. Duct leakage or system sizing. Leaky or uninsulated ducts in attics or crawlspaces, or an undersized unit, mean the system can never keep up during design-temperature days.

How to fix Rheem heat pump runs constantly: safe checks first

• Thermostat.
  • Confirm the mode is correct (Heat or Cool) and the fan is on AUTO.
  • Set a reasonable setpoint and replace the batteries if the display is dim or blank.
  • Check whether the thermostat says “Aux” or “Em Heat.” Emergency heat should not be on.
• Weather check. Compare current outdoor temperatures. Steady running in single digits through the 20s °F is usually normal.
• Air filter. Replace it if it looks gray or clogged, and confirm the airflow arrow points toward the blower.
• Registers and returns. Open all supply registers and clear furniture and rugs away from return grilles.
• Outdoor unit, visible exterior only.
  • Clear leaves, snow, and debris from around and on top of the unit, leaving about 2 ft of clearance.
  • Do not open the cabinet or spray inside it.
• Condensate line. Make sure the indoor drain line isn’t backed up and the pan isn’t overflowing.
• Unit won’t stop with the thermostat off. Shut it off at the breaker or the outdoor disconnect and call a technician. Don’t run it this way.

How a technician will diagnose it

A technician should work through these steps:

1. Confirm the thermostat call. They verify whether Y (and W) are energized when the thermostat is satisfied, which separates control-side faults from equipment faults.
2. Check the contactor. They inspect it for welded or pitted contacts and check coil voltage with the call removed.
3. Measure airflow. This includes static pressure, plus filter and indoor coil condition.
4. Measure refrigerant performance. They read pressures, superheat, and subcooling against Rheem’s charging chart for your model. If the charge is low, a leak search should come before any recharge.
5. Measure temperature split. They check supply and return temperatures in the current mode and compare them with expected values.
6. Check the reversing valve. They compare temperatures across the valve to detect internal bypass.
7. Read stored faults. For Prestige or EcoNet models, they review any stored faults on the board or thermostat.
8. Assess ducts and sizing. If the equipment checks out, they look at duct leakage and sizing, typically with a Manual J load comparison.

Be cautious of a quote that adds refrigerant with no leak search, or that recommends replacing the system before testing the contactor and charge.

Symptom, cause and what to do

Rheem heat pump runs constantly repair cost

Typical US ranges, including parts and labor:

Parts covered by Rheem’s registered warranty can lower costs, but labor and refrigerant are usually extra.

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