I have a 5 year old Dolphin S300i, which I love, and has worked very well until recently. It basically stopped moving. It will turn on and move and inch or two forward and then backward and then simply stop. I did the out of water test (positioning the cleaner upside down out of the pool) and it would move the tracks. So, I began troubleshooting by taking it apart. There is 110 VAC to the power supply and 29 VDC coming out. I disassembled the Dolphin and it was clean and the impeller will turn by hand. I did a continuity test on the cable and that was good. I also checked the DC voltage at the end of the cable to the motor and it was also 29 VDC. I had the motor completely out of the S300i and turned on the power. The drive gear began turning first for several seconds, reversed and them the impeller began spinning. Both the drive gear and and impeller turned for about 25-30 seconds before stopping. I believe that this is normal since it is out of water. This seems to tell me that the motor is good. I did take the rubber tracks off and the drive wheels. As you may know, the wheels and bushings are simply plastic (no bearings) and did seem a bit worn and sloppy. Can a Dolphin expert give me some hints or tips on the likely problem and/or further troubleshooting? I hate to simply start ordering parts to experiment. Thanks.