Back in July 2021 I replaced my Prowler 920 electronics with: 9995388-EX Motor Unit. This was after a failed attempt at cleaning the impeller motor. The first motor unit lasted about 3 years. The replacement motor unit lasted just over 2 years. The impeller motor in the replacement unit was different. As others have stated, the newer motor seems to go through brushes quicker. This time, I had a lot less carbon dust, but the brushes were definitely worn out. I opened the motor and used an air compressor and tooth brush to clean it as much as possible. I replaced the brushes and Mr. Roboto is now back in action.
Below are some tips:
Tip 1: I ordered the replacement brushes here (or I have 98 extra and I'm happy to mail you a set if you send me a message):
I used sand paper to sand to the correct dimensions (sanded the sides and the front) correct size seems to be: 6mm x 5mm x 12mm. I also used an X-acto and small screw driver to score a notch on the back side of the brush (to match the original brush). You can pull back the spring with a screw driver or small pliers temporarily to remove/insert the the brushes. I also saw impeller rebuild kits on eBay, but haven't tried these.
Tip 1: I wasted a lot of time because I re-assembled the motor with the permanent magnets in the motor housing 180 degrees rotated. This resulted in the impeller turning backwards (clockwise). It should spin counter-clock wise and expel water from the top of the robot vent and not suck in water from the vent. My robot was doing wheelies and flipping in the pool when the motor was turning backwards. I also struggled to get the screw back aligned. I recommend you put some painters tape on the motor housing and use a sharper to mark the orientation of the top and bottom pieces prior to disassembly. Place a dot on silver portion of the top and bottom and on the painters tape for ease of aligning the screws on re-assembly.
Tip 2: if you did not use the painters tape and are having trouble getting the screws back in then insert the motor in the housing, but not the piece with the brushes...use a flash light to look inside the motor, spin the top (silver) portion of motor until you see the screw holes between the opening in the magnets. You do NOT want the holes to be centered. You actually want the hole slightly right. This will allow the sides of the magnet to act as a guide for the long screws to slide down the side of the magnet and into the screw hole. If you center the hole, the magnets will pull the screw to the left/right and you will never get the screws into the screw hole. Note: I had a tough time loosening the two screws holding the impeller motor together. I ended up using my Milwaukee impact driver and it worked great
Tip 3: Don't bother removing the power cord from the motor unit. All this can be done with it intact
Tip 4: The brushes need to be de-soldered. You will want remove the small printed circuit board from the holder as the wires for the brushes are mounted through the board and soldered both the topside and bottom side. I was lucky that we have a nice setup at work. Remove the 2 small black screws. You will want either a solder sucker, solder wick or both to clean out the holes in order for the new wire to fit. There is a black strain relief holding the power supply wires in place..this slides easily out once you've removed the 2 screws.
Tip 5: Look carefully into the impeller motor housing as there is a round metal thin washer about the size of a dime that often comes off and sticks to the magnets. This goes into the center of the cap that holds the brushes..it fits underneath the brushes in the cap. The end of the motor has a bearing that will hold this in place when assembled. You'll need to set this washer in place while putting the cap with brushes back on the motor case.
Tip 6: During re-assembly the brushes will need to be pushed back to fit around the commutator bar. The long screws from the motor actually work well to do this. A magnetized screwdriver tends to cause the thin metal washer to come loose...which is why I used a screw. There is a hole in the bottom of the cap to provide access during re-assembly. Put the cap back on at a slight angle while using a screw (inserted through the hole in the bottom of the cap) to compress one of the brushes, once one brush is around the commutator bar, press firmly to hold the brush compressed against the commutator bar and then push the other brush in using one of the long screws as a tool and wiggle the cap on.
Tip 7: When reinserting the motor into the motor unit you will see part of the top of motor has a flat portion. In the motor unit you will see a corresponding flat piece of plastic...these need to be aligned. Once aligned you can push down firmly and the motor will pop up within the motor unit and slide the silver retaining ring back into place. I found it easiest to put the impeller motor on a flat surface and push the motor unit housing down on top of it. You should notice some springiness in the impeller motor while pushing down. If not, you don't have it aligned properly.
Tip 8: I recommend you apply some silicon to the O-ring in the motor unit housing and the O-ring on the top of the impeller motor. I used Magic Lube II. While debugging the motor running in reverse, I opened and closed the motor housing at least 4 times and ran the robot in the pool. In all cases I did not have any leaks. On the top inside of the motor unit the O-ring will fit into a sort of channel holding it in place while you join the two pieces back together. Align all the tabs, pushing easy at first. Once it looks aligned, push a corner and close the white retaining tabs...then go across to the other corner and do the same...work your way corner to corner until all white tabs are closed.
