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Fix a condensate pump that will not run

We'll confirm power, check the float switch, clear clogs, then isolate the cause—stuck float, failed pump, or wiring—or tell you when to call a pro.

Troubleshooting · Home maintenance
15–45 min
What you'll need
  • Screwdriver (for opening pump cover if needed)
  • Cup or jug of water (to flush inlet and discharge)
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Steps

Goal: Confirm the pump should run, then isolate the cause—power, float, clog, or pump failure.

  • Check the pump reservoir. If water is present but the pump does not run, the pump has failed or something is blocking it.
  • Good: Water in reservoir, pump not running—proceed to Check power and float.
  • Bad: No water in reservoir—check the drain pan and inlet line. See When to get help.

Check power and float

Goal: Rule out power loss and a stuck float switch.

  • Confirm the pump is plugged in and the outlet has power. Check the circuit breaker.
  • Manually lift the float switch. If the pump runs when you lift it, the float was stuck. Clean the reservoir and free the float.
  • Good: Pump runs when float is lifted—float was stuck. Free it and retest.
  • Bad: Pump does not run when float is lifted—proceed to Clear clogs.

Clear clogs

Goal: Clear the pump inlet and discharge line.

  • Disconnect the inlet line (from drain pan to pump). Check for blockage. Flush with water.
  • Disconnect the discharge line (from pump to drain). Check for clogs. Flush with water.
  • Reconnect and test.
  • Good: Lines clear—proceed to Pump hums but no water if the pump hums.
  • Bad: Pump still does not run—call a pro.

Pump hums but no water

Goal: Free a stuck impeller or identify pump failure.

  • If the pump hums when the float rises but no water moves, the impeller may be stuck.
  • Unplug the pump. Tap the housing gently. Plug back in and test.
  • Good: Pump moves water—impeller was stuck.
  • Bad: Still no water—motor or impeller failed. Replace the pump or call a pro.

When to get help

Call an HVAC professional if:

  • The pump has power and a free float but still does not run
  • The pump hums but no water moves after tapping (motor or impeller failure)
  • You are not comfortable working with electrical components

Verification

  • The pump runs when the float rises.
  • Water flows from the pump through the discharge line to the drain.
  • No overflow from the pump reservoir when the HVAC runs.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Confirm symptom Verify water in the reservoir but the pump does not run.
  2. Power and float Check outlet, breaker, and float switch—float must rise freely.
  3. Clear clogs Clear pump inlet and discharge line.
  4. Impeller If pump hums but no water, tap to free impeller or replace pump.
  5. Call a pro Pump still does not run, motor failure, or pump replacement needed.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Whether the pump has power
  • Whether the float moves freely
  • Whether the pump runs when the float is lifted manually
  • Inlet and discharge line condition (clogs)
  • Whether the pump hums but does not move water
  • Steps already tried

Is there water in the reservoir but the pump does not run?

The float must rise to trigger the pump. Water in the reservoir with no pump action means a fault.

Check the pump reservoir. Good: water in reservoir, pump not running—proceed to check power. Bad: no water in reservoir—condensate may not be reaching the pump; check the drain pan and inlet line.

Yes No

You can change your answer later.

Does the pump have power?

Check the outlet and circuit breaker.

Confirm the pump is plugged in and the outlet has power. Check the circuit breaker. Good: power on—proceed to check float. Bad: no power—fix outlet or breaker, then retest.

Yes No

You can change your answer later.

Fix power and retest

Plug in the pump or reset the circuit breaker. Confirm the outlet has power. Retest the pump. If it runs when the float rises, power was the cause.

Done

Does the pump run when you lift the float manually?

A stuck float prevents the pump from running. Lifting it manually tests the pump.

Manually lift the float. Runs when lifted: float was stuck—clean the reservoir and free the float. Does not run: pump may have failed—proceed to check clogs and impeller.

Yes No

You can change your answer later.

Free the float and retest

Clean the reservoir and free the float. Confirm it moves freely. Retest. The pump should run when the float rises.

Done

Are the inlet and discharge lines clear?

Clogs can prevent water from entering or leaving the pump.

Disconnect the inlet and discharge lines. Flush with water. Reconnect and test. Good: lines clear—proceed to impeller check. Bad: still clogged or pump does not run—call a pro.

Yes No

You can change your answer later.

Clear clogs and retest

Flush the inlet and discharge lines. Reconnect. Retest. If the pump runs and moves water, the clog was the cause.

Done

Does the pump hum but not move water?

A stuck impeller can cause humming without water movement.

If the pump hums when the float rises but no water moves, unplug it and tap the housing gently. Plug back in and test. Good: pump moves water—impeller was stuck. Bad: still no water—motor or impeller failed; replace pump or call a pro.

Yes No

You can change your answer later.

Tap the pump and retest

Unplug the pump. Tap the housing gently. Plug back in. Lift the float and test. If water moves, the impeller was stuck. If not, replace the pump or call a pro.

Done

Call an HVAC professional

Call an HVAC professional if the pump has power and a free float but still does not run, the pump hums but no water moves after tapping, or you are not comfortable working with the pump.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why would a condensate pump not run?
Common causes: no power (tripped breaker, unplugged), stuck or faulty float switch, clogged pump inlet or discharge line, or a failed pump motor. The float must rise to trigger the pump—if it is stuck or the inlet is clogged, the pump will not run.
Can I fix a condensate pump that will not run myself?
Yes. Check power, the float switch, and clogs first. Most issues are power, float, or clog related. If the pump hums but does not move water, the impeller may be stuck—tapping the pump sometimes frees it. Pump replacement may require a pro.
When should I call an HVAC professional for a condensate pump?
Call a pro if the pump has power and a free float but still does not run, the pump hums but no water moves (impeller or motor failure), or you are not comfortable working with electrical components.

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