A pool pump that won’t turn off on its programmed schedule almost always has a stuck mechanical timer tripper, a relay with welded contacts, or an automation system override commanding the pump to stay on. None of these are pump failures — the motor is just being told to keep running. Check the timer or controller before touching the pump itself.
This Is a Control Problem, Not a Pump Problem
I want to set expectations clearly: a pump that won’t turn off is being commanded to run continuously by whatever controls it — a mechanical timer, a relay, or an automation system. The pump motor itself is doing exactly what it’s told. Fixing this means fixing the control device, not the pump.
Repairing a pool pump that won’t turn off — diagnosing the timer and relay causes behind continuous running.
Mechanical Timer — Missing or Misplaced OFF Tripper
The most common cause on older installations. Open the timer box (power off, verified with a tester) and look at the metal trippers clipped to the dial wheel. If the OFF tripper has fallen off, is bent, or is oriented backward, it won’t actuate the switch and the pump runs continuously. Check that both ON and OFF trippers are present, clipped firmly, and the OFF tripper is set to your intended stop time. Replacement trippers run $3–8.
Relay Contacts Welded Closed
On systems using a relay to switch pump power (common with digital timers and automation controllers), the relay contacts can weld together from repeated arcing over years of cycling — especially under the high inrush current of a motor starting. A welded relay passes power continuously regardless of the control signal. This requires relay replacement, not repair — $15–40 depending on relay type and amperage rating.
Digital Timer or Automation Override
If you have a pool automation system (Hayward OmniLogic, Pentair IntelliCenter, Jandy AquaLink), check for an active manual override or “service mode” that’s commanding the pump on regardless of the programmed schedule. Most systems have a clearly labeled override function — sometimes left on accidentally after maintenance or troubleshooting. Check the system menu for any active override before assuming a hardware fault. See our automation guide for system-specific menu navigation.
Digital Timer Lost Its Schedule
A digital timer that lost power or had a firmware glitch can default to “always on” if the schedule data was corrupted. Reprogram the schedule from scratch, including the current day and time — don’t assume the existing program is intact just because the display looks normal.
Manual Override Switch Left On
Some installations have a manual on/off switch separate from the timer, intended for override during maintenance or pool parties. Verify this switch is in the AUTO or TIMER position, not manually held ON — an easy thing to forget after a repair or cleaning session.
Frequently Asked Questions
Is it bad for my pool pump to run constantly?
Not mechanically harmful in the short term — pool pumps are designed for continuous duty. The real cost is electricity: a single-speed pump running 24/7 instead of 8 hours costs roughly 3x as much per month. Fix the control issue to restore your intended schedule and save on the electric bill.
How do I know if it is the timer or a relay causing this?
Open the timer box and visually inspect the trippers first — that’s the simplest cause to rule out. If trippers look correct and properly set, the issue is likely a relay or automation override further upstream. A multimeter continuity test on the relay (with power off) can confirm whether contacts are stuck closed.
My pump will not turn off and I do not have a mechanical timer — what do I check?
Check your digital timer or automation system’s programmed schedule and look for any active manual override or service mode. Power cycling the automation controller sometimes clears a stuck override condition.
Can a stuck pump cause damage if I do not fix it right away?
No immediate damage risk from the pump running — but continuous unintended operation costs real money in electricity. There’s no urgency from a safety standpoint, just a financial reason to fix it promptly.
I fixed the timer trippers but the pump still will not turn off — what is next?
Check whether power is actually being interrupted at the timer by testing voltage at the motor terminals when the timer should be in the OFF position. If voltage is still present, the problem is downstream of the timer — likely a welded relay or a wiring fault bypassing the timer’s switching function.