Robotic pool cleaner not working: 11 fixes to try

Common symptoms

• The power supply or control box shows no lights at all.
• The robot hums or blinks but does not move.
• It starts, then stops after a few seconds and shows an error light.
• It drives in circles or only turns one way.
• It cleans the floor but will not climb the walls.
• It moves but leaves dirt behind, or only cleans part of the pool.
• The floating cable keeps twisting and tangling.

Quick checks before anything else

• The outlet has power and its GFCI has not tripped.
• The power supply is switched on and plugged straight into the outlet, with no extension cord.
• The floating cable is pushed all the way into the power supply.
• The filter basket or canister is empty and rinsed.
• Nothing is wrapped around the impeller, tracks, wheels or brushes.
• The pool walls are not slimy, and no clarifier or flocculant went in recently.
• A cordless robot is fully charged.

What causes a robotic pool cleaner to stop working?

• No power No lights on the power supply: a dead outlet, a tripped GFCI, or a loose cable plug.
• Clogged filter The robot circles, will not climb, or misses dirt. Dolphin’s power supply shows an orange light for this.
• Debris in the impeller Hair or leaves in the impeller (the small pump fan) cause circling, one-way turning and weak suction.
• Air trapped inside The robot floats, or stops soon after starting with a flashing light.
• Slippery walls Algae you cannot always see makes the robot slide off the walls.
• Cable twists or bad placement The robot tangles itself or cleans only part of the pool.

Step-by-step: robotic pool cleaner troubleshooting

When a robotic pool cleaner is not working, we start with power, then the parts you can clean by hand, then the water and the cable. These steps follow the Maytronics Dolphin M600 and Polaris 9350/9450/9550 Sport manuals. Other models are similar, but check yours for its own limits. Unplug the power supply before you open or touch the robot.

1. Check the outlet and GFCI. Dolphin’s first checks are voltage at the wall socket, the power supply switched on, and the power cable pushed fully into the power supply. If the power supply’s ground fault interrupter has tripped, Dolphin says to turn the power supply off, wait 30 seconds and turn it back on. Both makers say never to use an extension cord. If the GFCI trips again on its own, Dolphin says to stop using the power unit and contact the maker.
2. Reseat the floating cable. Both manuals list a floating cable that is not fully plugged into the power supply as a reason the robot will not move or flashes an error right after start. Unplug it, check the pins for corrosion or a bent pin, and reconnect it. On a Polaris, the connector screws in; Polaris says to screw it in all the way so no gap shows.
3. Get the air out. Polaris says its robots stop by themselves if they run without being fully under water, and that flashing lights during a cycle can mean the cleaner sucked air for 60 seconds. Lower the robot into the pool and hold it upright so trapped air bubbles out, then let it sink to the floor. If it floats, repeat.
4. Clean the filter. Dolphin recommends cleaning the filter basket after every cycle, and Polaris says to clean the filter canister after each use. Both troubleshooting tables list a clogged filter first for a robot that will not climb, and Dolphin lists it first for one that drives in circles. Hose the panels before they dry out, as Dolphin advises, and take apart and clean the fine filter panels at least once a month.
5. Clear the impeller. With the power unplugged, open the impeller cover and pull out hair, string or leaves. Dolphin lists impeller debris for a robot that circles, turns only one way, or moves without cleaning. Polaris says to check the pump axis, propeller and fan for debris and hair.
6. Free the tracks, wheels and brushes. Check that nothing blocks the tracks or wheels. Polaris says to turn each wheel a quarter turn at a time in one direction until it moves smoothly, then do the same in the other direction. Brushes worn smooth, or showing their wear marker, and worn tires both cost grip, and Polaris says to replace them.
7. Fix slippery walls and water balance. Dolphin and Polaris both say algae makes walls slippery, even when the water looks clear. Polaris’s fix is a shock treatment and a slight pH drop, with the robot out of the pool; Dolphin says to adjust the chemistry and scrub the walls. Our green pool water guide covers clearing algae, and pool chemistry covers keeping pH in range. Dolphin also notes climbing can suffer in water below 59 F.
8. Untangle the cable and move the power supply. Place the power supply so the robot can reach the whole pool. Polaris says the cable should enter the water near the middle of the pool’s length, with only enough cable in the water to reach the far end. To take out kinks, Dolphin says to stretch the cable flat in the sun for at least a day.
9. Read the error light or code. On a Dolphin, a steady red light is a robot error; if the steps above do not clear it, Dolphin says to contact your dealer. On a Polaris 9450 or 9550 Sport, codes 1 to 3 point to a short in the pump or a drive motor, 4 to 6 mean a motor is working too hard (often hair or debris), 7 and 8 mean the robot floated or ran out of water, and 9 is just the end of a cycle. Press any key to clear a Polaris code after you fix the cause.
10. Reset the cycle. For a Polaris that will not start, its manual says to turn the wheels, unplug the control unit, wait at least 20 seconds and plug it back in. For a Dolphin, turn the power supply off and back on. App-connected models may also need the app or Wi-Fi reset steps in their own manual.
11. Charge a cordless robot fully. A cordless robot runs on its battery, so one that will not start may only need a full charge on its own charger or base. Check the charger’s lights and the contacts on the robot. The charge time and what each light means are in your model’s manual.

Dolphin vs Polaris vs cordless robots

Ppm means parts per million, the unit test kits use for chlorine and salt. Corded Dolphin and Polaris robots get most of their trouble from the floating cable and power supply placement. Cordless robots skip the cable, so a robot that will not start is often a charging problem. Suction cleaners are a different machine that runs on your pool pump; our pool lights and cleaners hub covers those.

When to call a pool or spa pro

• The GFCI trips again after a reset. Dolphin says to stop using the power unit.
• A Dolphin keeps a steady red light after you cleaned the filter and impeller.
• A Polaris shows code 1, 2 or 3 again after you cleared debris and checked the cable pins.
• The floating cable or power cord is cut or damaged. Polaris says not to repair the cleaner, control unit or cables yourself.
• The motors run but the robot will not move, with nothing caught in the tracks.

Common questions