First, thanks to all for the great info on this site. It gave me the courage to fire the pool service (who as near as I can tell, never tested the water one time in the six months they worked for me!).
Two questions regarding the sweep.
1. It says Polaris, but no other identifying number or otherwise that I can find, inside or out. Blue and white. Three wheels. I know if I did a Google image search and looked at every possible model I could probably find it, but if there is one site that shows most (all) Polaris models, regardless of age, so I can determine which it is, that would be very helpful. Pool is something less than 20 years old, but of course that doesn't mean anything regarding the age of the sweep. And I was given no "history" or manuals.
2. The sweep wheels do not turn when the pump is on. This is a new event. Previously worked fine. With the sweep out of the pool and the pump OFF, the wheels turn with what I think is normal resistance (due to the high gear ratio between the wheels and the impeller). I partially disassembled it and impeller and gears seem to turn freely and drive the belts and wheels with no resistance on the impeller, and manually turning the impeller (very easy to do) turns the wheels with no abnormal resistance, but when I reassembled and put it the water, turned the pump back on, the wheels just sit there (will manually turn so not "frozen"). Appears to an amateur like myself, that there is ample water flow from the pump ... vacuum portion works fine, sweeper tail has good flow, direction nozzle has good flow. Although I don't know anything about anything, it just seems that it is a simple mechanical device that converts water flow into circular then gear driven motion.
Professional help is greatly appreciated!