The power selector on my Miele s8310 power plus starts on full power and drops down to upholstery mode. Have changed bags and filters.

SOURCE: stopped working - warning light on

There is an electronic circuit board on the motor that may have gone bad and will have to replaced, part # 06836740 and sells for around $75.00, for model S516. But if this a S316, then it could be the speed control mounted on the motor, Part # 04416342 and sells for around $83.00. Both of these models are Cat Naad Dog so you need the model number berfore you order a part.

SOURCE: my Miele vacuum full bag indicator

Check the suction at the vac, without the hose, if it is strong, then you hose is clogged. If it is weak, filters could be the problem, one is the back where the bag sits, the other is on the top, you can see it when you raise the lid.

SOURCE: My Miele cat & dog

Will it power up without the hose attached? If it does then you have a clogged hose. If not, there is a circuit board by the motor that may be bad.

SOURCE: Electrical power down while vacuuming (not a reset)

Thank you JonahBegone!
My 4 years old Silver Moon has been power down off and on for a couple of months, but all of sudden it kept doing it. Then the power won't turn on when I plugged it in ( this turns out to be another problem, see my other posting). I took your advice on taking the hose and handle apart. I unscrewed the 5 screws, but can't pull the handle apart to look inside. I was able to see the 3 metal contact on the hose that you mentioned through a 1/4 inch gap when I forced the handle apart. I cleaned the black stuff off through the little gap by rotating the hose a few times. Then magically, my power down problem also went away. Thank you once again.

SOURCE: Miele 5000 vacuum cleaner stopped during use. no lights on

could be your retractable cord assembly's contacts..

push the power on while pulling out the cord. see if it tries to start.