How to repair a Maytronics Dolphin robotic pool cleaner that quits early

by TheHobe
(Los Altos CA)

Maytronics Rev 03 Control Board

This is a long story. My Dolphin Advantage failed after infrequent use over a period of 8 years. The unit still looks almost new, not like the used ones for sale on Ebay that have been out in the sun for 5 years. The time of operation slowly decreased from the normal 3 hours to 15 seconds. After visiting this site, I was encouraged to look deeper since I had effectively paid $5-$10 for each time I had run my unit. Although the units do a good job of cleaning the pool, this is too expensive in my opinion. I looked to Maytronics for help but they do not support their products very well. You even have to pay your own shipping for repair in warranty as I understand it.
The motor driving unit sells from different sites over a $300-$600 range. The motor units have 2-3 motors and a control board. The motor unit can be removed quite easily by removing the plastic motor screen (2 screws) and the motor securing screws (4, 2 on each side of the Dolphin handle,use a small needle nose pliers to extract the screws after they are loose). Rotate the drive belts until the drive shaft slot allows you to lift the motor from the mounting position. Now lift and rotate the motor housing a little to extract the motor from the unit being careful to not overstretch the wiring to the motor housing. Upon disassembling the motor unit by removing the many screws and using ONLY the slots on either end of the motor unit case with two screwdrivers. Be very careful while prying up the motor case top not to gouge the sealing surface.

Once you open the motor housing, check for any water or sandy stuff (actually desiccant pack contents). If there are sign of water, it may not be the rubber seal that you would first suspect. I found out after many experiments that the motor case (on more than 1 unit I have opened) develops a stress crack radially emanating from the drive motor case opening hole towards the open top of the case. This is a very fine line crack that you will not see unless you are looking for it. I took out 3 tracks motors on 3 units and found this crack. You must repair this leak if you have any chance of repairing the unit. I think this is why Maytronics only supplies full, new motor units instead of internal parts for repair. I used a plastic welding wicking cement normally used for plexiglass and then cover the entire area with a GE 50 year kitchen and bath RTV after reinstalling the motor.

There are other potential electronic problems as well with the control board. These include the motor current sensing resistors 0.1 Ohm and 0.5 Ohm and the 18 Ohm resistor used in conjunction with a dual Dmos device Si4956 or Si4980. I have posted previous messages on this board discussing these weaknesses.

After fixing the leaking motor housing and replacing the parts listed above I could not get the Dolphin to work properly UNTIL I replaced the original Belts, axles, and drive cog wheels with the "Maytronics Upgrade Drive System", obviously the manufacturer realized they had a problem with their original drive belt system. My Dolphin now runs for 3 hours and 15 minutes, maybe longer than when I first ran the unit when new!