A pump that won't start isn't one problem. It's four, and the way it fails tells you which one you've got. So before you reset anything or open anything, stand at the pad when it should be running, and listen.
Key takeaways
- Silent, humming, tripping and shutting off hot are four different faults. Work out which one you have before you touch anything.
- A variable-speed pump stopped from its own keypad stays stopped. On Hayward's 400, 600 and 800 series, STOP has no time limit and the schedule won't restart it.
- A GFCI that trips when nobody pressed its test button means current is reaching ground. Hayward and Pentair both say don't use the pump until it's fixed.
- A hum with no spin is a jam or an electrical fault. With the breaker off, turn the shaft by hand: stuck points at the pump, free points at the motor's electrics.
- A single-speed motor that stops and restarts by itself is its thermal overload doing its job. Hayward, Jandy and A.O. Smith all point at low voltage and blocked airflow.
Match what it's doing
| What it means | Check first | |
|---|---|---|
| Silent. No lights, no hum | No power is reaching the motor, or nothing is telling it to run | Timer or schedule, then the breaker |
| Silent, but the keypad is lit | The pump has been stopped, or it is waiting for its next schedule | The keypad's stop button and the schedule |
| Hums, but the shaft never turns | Power is there, but it can't rotate | Turn the shaft by hand with the breaker off |
| Trips the breaker as it tries to start | It is drawing far more current than it should | The same checks as a hum |
| Trips the GFCI | Current is leaking to ground | Nothing. This one is an electrician's |
| Runs, stops, restarts by itself | The motor is overheating and protecting itself | Airflow around the motor, then voltage |
| Keypad flashing or showing a code | The drive has stopped on a fault | Read the code before you reset it |
One thing before any of it. A motor that isn't running isn't necessarily off. US Motors, which makes pool pump motors, puts it bluntly in its troubleshooting guide: a motor that isn't running does not mean the power is off. A variable-speed pump waiting for its schedule is live. So is a single-speed motor sitting out its thermal overload, and Hayward's manual says that one restarts on its own once it cools. Anything past the breaker and the reset button starts with the breaker off.
It's silent
No hum, no lights, nothing. Either nothing is telling the pump to run, or the power isn't getting there. Check in that order, because the first half needs no tools.
Is it supposed to be running right now?
- A mechanical timer. Push the manual lever. If the pump starts, the switch works and the problem is the clock or the trippers. How a pool timer works walks through both. Hayward's troubleshooting says the same thing in fewer words: make sure the timer works, and bypass it if you need to.
- An automation panel. Check it isn't in a service or hold mode. On a Pentair EasyTouch, schedules don't run at all in Service mode, and Time Out mode suspends them for several hours. The automation guide covers the other systems.
- A variable-speed pump running its own schedule. Jandy's manual for the VS FloPro says it plainly: the motor only turns on during the times programmed into the controller. Check the schedule covers now.
Has someone stopped it? Variable-speed keypads have a stop button, and a stopped pump stays stopped. On Hayward's 400, 600 and 800 series, the fourth press of the override button is STOP, and it has no time limit. The pump stays off until someone cancels the override. The older TriStar VS has a Stop/Resume button that holds the pump off until it's pressed again. On Pentair's IntelliFlo3, a solid red light on the ON/STOP button means the pump is disabled, and solid yellow means it's idle, waiting for its next program.
It's the first thing I check on a variable-speed pump, because it's the one that costs nothing. Somebody cleaned the basket, hit stop, and forgot.
Then the power.
- The breaker. US Motors' instruction for a tripped one is to push it all the way to off, then back on. A tripped breaker can sit between the two and pass for on.
- The GFCI, if the pump is on one. Press reset once. If it trips again, stop there and read the GFCI section below.
If the breaker and GFCI are both on and it's still dead, the next check is voltage at the motor. That means a meter on live terminals, and it's an electrician's job. US Motors' guide says what they'll be looking for: loose or corroded connections at the motor, and even insects nesting in the wiring. If power is reaching the motor and it makes no sound at all, US Motors says there may be an open circuit inside it, and a new motor is likely.
It hums but won't spin
A hum means power is reaching the motor and the motor can't turn. Don't stand there resetting it. Turn it off at the breaker. If the motor's hot, A.O. Smith's motor manual says to let it cool before you try again.
Then turn the shaft by hand, with the breaker still off. Hayward and US Motors both start here. US Motors says to work from the back end of the motor. Some take a 5/16-inch hex key in a socket in the end of the shaft. On Jandy's VS FloPro it goes through the back of the fan housing. On Hayward's 400, 600 and 800 series, you take the OmniX module off to reach it.
It won't turn. The problem is in the pump, or in the motor's bearings. Hayward's troubleshooting gives one cause for a hum with no start, an impeller jammed with debris, and says to have a qualified repair professional open the pump. US Motors adds a tight pump seal, something lodged in the pump housing, and a bad bearing. If there's a lot of debris in there, Jandy's advice is to check the strainer basket for breaks, because that's how it got in.
It turns freely. The pump isn't what's stopping it, so it's electrical. US Motors' list: wrong connections, low voltage, a fault in the windings, an open start switch, loose capacitor connections or a failed start capacitor. Every manufacturer here wants the voltage at the motor within 10% of the nameplate. A motor that's starved of voltage can hum and go nowhere.
The capacitor
A single-speed motor can have two capacitors. US Motors describes the start capacitor as the black cylinder on the back of the motor that gives it the extra push it needs to start. The run capacitor, in a steel case, helps it run efficiently. A failed start capacitor usually shows a burned hole between its terminals. A run capacitor bulging at its terminal end is, in US Motors' words, sometimes a sign of failure.
If it's the capacitor, that's the good news. It's a small part, and you keep the motor.
US Motors and A.O. Smith publish the same test. Power off. Take the leads off, and discharge the capacitor by bridging its terminals with the metal of an insulated screwdriver. It may pop. Then put an ohmmeter across the terminals on its highest setting:
- Drops toward zero, then climbs slowly: the capacitor is probably fine.
- Drops to zero and stays there: shorted.
- Stays high: open.
Replace a bad one with a capacitor of the same microfarad and voltage rating, which is printed on it.
It trips the breaker or the GFCI
Two different devices, and two different messages.
A breaker trips on too much current. A pump that trips it as it tries to start is doing a louder version of the hum: A.O. Smith's manual puts humming, trying to start, blowing a fuse and tripping the breaker under one heading, with one set of checks. Work through the hum section above. A.O. Smith also lists an overloaded circuit, undersized wiring and a burned start winding. Once the shaft and the capacitor check out, it's an electrician's.
A GFCI trips when current leaks to ground. It's the device that protects people, and it's the one not to argue with.
Resetting it until it holds isn't a fix. If the pump has been flooded, or has been leaking at the seal, tell the electrician. US Motors traces nearly half of all pool pump failures to leaking pipe joints and pump seals, and that water goes somewhere. Pentair says never to run a pump that's been flooded, and what a leaking pump is telling you covers where the water gets in.
Every manual here requires the GFCI. Hayward, Pentair and Jandy all say to connect the pump only to a GFCI-protected circuit, and Jandy's manual adds that the National Electrical Code requires one on every pool pump circuit. Pentair also wants the pump on its own independent circuit, unless it's paired with Pentair's salt chlorine generator.
Test it now and then. Press test, and the power should cut. Press reset, and it should come back. Hayward says that if it doesn't, the GFCI itself is defective. If your pump has no GFCI at all, that's worth an electrician's visit on its own.
It runs, then shuts itself off
A single-speed motor has an automatic thermal overload. Hayward's manual explains it: when the supply voltage drops, the protector shuts the motor off before heat can build up enough to burn out the windings, then lets it restart once it cools. It'll keep cycling like that until the cause is fixed.
The manufacturers point at the same few causes:
- Low voltage. Hayward says it's frequently undersized wiring or an extension cord, and its manual forbids extension cords outright. The motor should see within 10% of its nameplate voltage while it runs.
- Blocked airflow. Leaves, mulch, grass clippings, or a cover pulled down too tight. A.O. Smith says to leave space between any cover and the motor. US Motors says not to wrap a motor in plastic at all, because it can cause rust and stop the motor cooling properly.
- Too much load. US Motors' line is amps more than 10% over the nameplate figure. A.O. Smith's list includes an impeller rubbing, a tight seal, and an impeller that was recently replaced and may be the wrong size.
Hot isn't the same as overheating. US Motors says every properly working motor is too hot to touch, with the shell at about 120°F. It's hot and cycling, or hot and smoking, that means trouble.
A variable-speed pump reports the same problems as faults. Pentair's manuals list an over-temperature fault, dealt with by blowing the dirt out of the motor's fan cover with compressed air, and an over-current fault, which means checking the rotating parts for debris. After an over-current fault the pump tries again on its own a minute later. When it overheats, the IntelliFlo3 slows itself down first to cool off, stops only if that isn't enough, and starts again once it has cooled. Hayward's older TriStar VS says to check the air temperature around the drive against its nameplate, 50°C or 122°F. Jandy's troubleshooting for a VS FloPro that gets hot and shuts off periodically is the same as for a single-speed: room around the motor, then voltage.
If it's an SVRS pump, there's one more reason it stops. SVRS stands for safety vacuum release system, and it shuts the pump off when it senses a blocked suction outlet. On Hayward's TriStar VS SVRS models, the pump restarts after 15 minutes, or only when someone presses Stop/Resume if it's set to manual. Find out what tripped it before you restart it. Pool drain safety explains what it's watching for.
Variable-speed pumps: read the light first
A variable-speed pump tells you far more than a single-speed ever could, if you look before you reset. Write down what it's showing.
Hayward's 400, 600 and 800 series (the TriStar VS 800, MaxFlo VS 400 and Super Pump VS 600) flash the ring light a set number of times:
- 1: DC voltage out of range. Check the line voltage is within 10% at the terminal block, and that the voltage jumper matches the supply.
- 2: motor current too high. Check for binding in the impeller, diffuser, seal or motor.
- 3: the drive has overheated. Clear its airflow path.
- 4: the pump stalled or couldn't start. Check for binding, as for 2.
- 5: internal motor or drive failure. Hayward says to call its technical service.
- 6: it has lost contact with the OmniX module. Check the module cable is plugged in.
These pumps have one more quirk. If the ring light is blinking after a power cut, the pump may be waiting for you. Hayward's fix is to press the pump's button.
Pentair's IntelliFlo3 uses the ON/STOP light. Blinking red is an alarm, and the pump stays stopped until it clears. Blinking green and yellow is a warning. The code itself shows in the Pentair Pool app, on an automation panel or on the optional touchscreen.
Jandy's VS FloPro shows faults on its controller. If the controller can't see the motor at all, Jandy's manual goes to the low-voltage RS-485 wiring and the drive's DIP switches, which have to be set right for the controller to find the pump.
Hayward's older TriStar VS, the one with a display, shows Check System messages instead. DC voltage too high or too low, drive overheated, drive overload, pump stalled and pump failed to start map onto the same checks as above.
To reset any of them, turn the power off at the breaker and wait. Hayward says until the light goes out, at least 60 seconds. Pentair's IntelliFlo3 manual says one minute. Jandy says at least five minutes, so the capacitors drain completely. If the same code comes straight back, Hayward says the problem may be inside the motor and drive.
A pump you just installed
If it's brand new and won't start, check the hookup before you blame the pump.
- The voltage setting. Many pumps run on either 115 or 230 volts and come set for one of them. Hayward's 400, 600 and 800 series come set for 230 with a jumper, and Pentair's WhisperFlo motor has a voltage selector switch. US Motors says a motor wired for 230 on a 115-volt supply may only hum, cycle or not start at all. Wired for 115 and fed 230, it says to expect sparks and smoke, and a failed motor if it isn't switched off quickly.
- The wiring. Hayward and A.O. Smith both say to match the connections to the diagram on the motor's nameplate.
- The shaft. US Motors says to make sure it turns freely by hand before the first start.
- On automation, Jandy's VS FloPro has to be set to the right pump number with its DIP switches, or the controller won't find it.
Where to stop and call someone
Resetting a breaker once, checking a timer or a keypad, and turning a shaft with the power off are yours. Past that:
- Anything that needs a meter on live terminals is an electrician's.
- A GFCI that won't hold is an electrician's too, and the pump stays off until it's found.
- Opening the pump to clear a jam is where Hayward sends you to a qualified professional. If you've changed a shaft seal before, it's the same teardown, and the TriStar VS page has the left-hand-thread impeller screw that catches people out.
- A motor with power at its terminals and no sound, or one that still hums with a good capacitor, is usually a new motor.
If it's the motor, the replacement may not be the kind you had. Pool pump motors from 1.15 to 5 total horsepower made since September 29, 2025 have had to be variable speed, which the variable-speed conversion guide explains. How to replace a pool pump covers whether to swap the motor or the whole thing.
And if it turns out the pump starts fine but won't move water, that's a different problem: a pump that won't prime starts on the suction side.
Frequently asked questions
Why won't my pool pump turn on?
Start with whatever is supposed to switch it on: a timer that has lost time, an automation schedule that isn't running, or a variable-speed pump someone stopped from its keypad. Then check the breaker and the GFCI. If the pump hums instead of staying silent, power is reaching it and something is stopping it turning, which is a different set of checks.
Why does my pool pump hum but not start?
Power is reaching the motor, but it can't turn. Hayward's manuals put that down to an impeller jammed with debris. US Motors, which makes pool pump motors, adds a seized bearing, low voltage, loose wiring and a failed start capacitor. With the breaker off, try turning the shaft by hand. If it won't move, the problem is in the pump. If it spins freely, it's electrical.
Why does my pool pump keep tripping the GFCI?
A GFCI trips when current leaks to ground. Hayward and Pentair both say that if it cuts power without anyone pressing its test button, there's a possibility of electric shock, and the pump shouldn't be used until a qualified person finds the fault. Resetting it until it holds is not a fix.
Why does my pool pump run for a while and then shut off?
On a single-speed pump, that's the motor's automatic thermal overload. It shuts the motor off when it overheats and lets it restart once it cools, over and over until the cause is fixed. Low voltage and blocked airflow around the motor are the first things to check. A variable-speed pump does the same thing through a fault code, and Pentair's restart by themselves once the fault clears.
How do I reset a variable-speed pool pump?
Turn it off at the breaker and wait before switching it back on. Hayward says to wait until the light goes out, at least 60 seconds. Pentair's IntelliFlo3 manual says one minute. Jandy says at least five minutes, so the drive's capacitors drain completely. If the same fault comes straight back, the reset hasn't fixed anything.
Can I replace a pool pump capacitor myself?
On a single-speed motor it's a replaceable part, and the motor makers publish how to test one. Power off, discharge it across its terminals with an insulated screwdriver, and check it with an ohmmeter. A bad one gets replaced with one of the same microfarad and voltage rating. It can hold a charge with the power off, so if that procedure isn't familiar, it's a job for a technician. Don't open a variable-speed drive at all.
