In the secondary market that I sell into, one of my most successful products is the Hoover Windtunnel bagged, self-propelled (U6400) series. They have excellent suction, for their price point they are reasonably rugged, they are fairly easy and economical to repair, people like the optional self-propulsion feature, bags are inexpensive and widely available. They offer buyers an option in a pantheon of new machines where few bagged upright vacuum cleaners are currently found.
From the standpoint of refurbing, the bagged SP Windtunnels are less problematic than the bagless. The latter have a diverter valve mechanism in the floor nozzle that is more commonly broken and expensive to repair.
The most commonly broken part in the Windtunnel bagged SP upright is the actuator arm for the controls on the SP feature. 90% of the machines I work on have this part broken. And if it looks intact, take a second, closer look, because it's likely to be cracked where it's difficult to see. Part is cheap and fairly easy to replace w/o removing the drive from the nozzle frame.
Some customers buy the less fancy non-SP bagged Windtunnel, preferring its net lighter weight to the SP model. Usually this involves women or stair issues. The non-SP Windtunnel has the same impressive suction that the SP has.
The Windtunnel name signifies a patented design in the area of the floor nozzle, so any Hoover upright (or canister w/ Windtunnel floor nozzle unit) that incorporates this design can rightly be called by the name. That includes some of the newer, Chinese-made machines. Of these, I've worked on some of the different UH-70000 series models but without much conviction. As refurbed, second-hand mdse., they sell reasonably well but I believe only because they "look newer." If you demonstrate and explain technical differences, some buyers will be receptive, others will still go strictly by appearance. And that conundrum describes selling consumer goods in a nutshell.
