Polaris 9300 failed troubleshooting motor box


Jun 28, 2016
Montreal / Canada
My trusted Polaris 9300 series failed after about 4-5 years of operation. Spoiler: I was getting lazy and leaving the robot for long period in the pool. Water got in the motor assembly.

I noticed the robot was getting weaker and this week it just turned on, advanced for a few feet then the two led start blinking in alternate fashion.

I took apart the control box and robot. Tested the floating line passed continuity test on all 3 pins.

Brought the motor assembly to my local Polaris dealer after two min he said motor unit is dead. $450 for the replace part.

There are no serviceable parts.

I opened the motor. 1st sign of trouble water started to leak out as I undid the motor assembly screws.

It was a real mess inside, every covered by carbon from the motor brushes, a bit of water. I cleaned everything. but found some corrosion on the control board.


All of the motors run on 24 volts. the main motor was easy to take apart and clean. The two small motors are sealed. After cleaning everything I connected all the parts turned on the control unit. Main motor starts and works for 15 seconds then control unit flashes error. As the main motor was working, I placed each of the small motors one at a time on the Pin connector made for the main motor, each of the small motors worked when connected here.

When each wheel motor is discontented the voltage reading on the pins is 27 VDC. when the motors are connected the voltage drops to 0. I'm wondering if this means the motor are damaged too much resistance or is the control board damaged.

Also I wish I would have tried this when the robot was still working out of water after power-on do the wheels turn after the main motor starts ? And how does the unit know its underwater. I did not find any water sensor.

On the control board I traced all of exposed pins in the areas with corrosion and I could not find any shorts. Does anyone know of any business which sells or repairs the control board or the small motors ?


Finally point, seeing how this unit is made I will never leave it in the pool, and I would take it apart every year to clean the motor unit. All that accumulation of carbon can't be good over time. It would have been nice if they had used brush-less motor in here.



Jun 28, 2016
Montreal / Canada
You can try https://circuitboardmedics.com . I used them to repair a KitchenAid control Board in my built-in Fridge. They did a great job for about $100. Fast turn around.

Thank you for the lead. I am really struggling with the decision trying to fix this robot. I am sure my local pool store throws away the broken robots customers bring for an estimate when they die. I have to ask if can sell me some dead one, but they probably won't dead one when they can sell a motor for $450.

I read that the replacement motors gear box kit from Polaris only has 90 days of warranty and the reviews on Amazon are not good.

I did find a thread on a RC group about a fellow who found a suitable replacement for the wheel motors : Complete Newbie trying to solve a problem - RC Groups.

Mabuchi RS-385PH-10280 DC Motor 24V, 150mA $8.95 USD per motor a bargain !

Mabuchi RS-385PH-10280 DC Motor 24V, 150mA ( 28M121 )

But in my case I still don't know if my control board is fried or not.

I would really like to know, if some can test this, Out of the water if you turn your Polaris 93xx 94xx or 95xx do the wheels start turning after about 10 seconds ?

Edit: I was able to test one of my wheel motors on 8 Volt battery it draws 150 mA and turns at a slow speed. Again when plugged to the control board, voltage goes from 28 V to 0 and Amp meter shows no current. Very strange, I really think the control board is broken.