Friday, January 15, 2016

Miele S2 Momentum Vacuum Cleaner Service Note

The Miele S2 Momentum is a fine piece of high-tech machinery; that is to say that it's largely unrepairable by conventional means in a home workshop. If the machine's electronics or motor develop a problem, you'll be out of luck -- you'll have to take it to a shop that's equipped to deal with the machine's architecture. However, it's still worthwhile to check out a dead machine's fundamentals -- even sophisticated machines are prone to simple failures.

Our unit died on us recently, and the trouble turned out to be an open circuit condition due to a line cord plug defect. Here's a view of what I discovered within the line cord plug.

The plug's neutral tine had fractured within the plug's encapsulation. When I cut and filed away the plug's encapsulation, the neutral tine came away with just a nudge. A conventional, screw-terminal Leviton plug from Canadian Tire made for a neat repair, like so.

The machine is back in business at very little cost. A factory-authorized repair outlet would no doubt have insisted on replacing the entire cord reel assembly to effect a repair -- easily a $100.00 repair job, more than likely.

I had to open up the machine in order to do a continuity test on the line cord. The casing has some concealed claws that make access a bit of a challenge, but once you know about them, it's not too difficult to get the machine opened up. Proceed as follows to open up the machine.

Filter Bag and Filters

Remove the filter bag.

Remove the exhaust filter. (The rectangular filter up on top.)

The remaining rectangular filter in the rear wall of the filter bag compartment can stay in place. (It's the motor pre-filter.)

Lid Removal

Spread the lid at its hinged pivot-points to free the lid from its hinge pins.

Upper Shell Fasteners

There are seven obvious screws to be removed. You'll need a T20 Torx driver. The screws are all the same length.

Foot Switch Cap

This is the tricky part. It's pretty much impossible to show by way of a photograph how this item is fastened. There are four concealed claws at the rear that must be unlatched -- two that keep the foot pedals from flipping up, and two that retain the entire cap.

Start by forcefully raising the front of the foot switch cap with your thumbs. It will snap free upward, getting you to here.

Note that the cap is now tipped up at the front by about one inch from its normal, seated position.

Near the centre-rear of the two 'pedals', there are two claws that keep the pedals down in place. Trip those two claws with a small screwdriver, and you'll get to here.

Now, looking down into the rear of the machine, you'll be able to see the two claws that are holding the rear edge of the cap in place. Trip those claws with a screwdriver, and you'll be able to free the cap completely. Here's what you'll see.

Unlatch the white cover, and you can tip it up to your right, like so.

Free the cable, circuit board and switch from the white cover.

Free the white cover from its hinge pins.

Upper Shell

Down inside a deep well, you'll see one last screw to be removed. With that screw out, pry up the upper shell at the front of the handle to free the front edge of the upper shell. There's also one claw-tower near the rear of the filter bag compartment. Trip that claw, tug the shell forcefully upward and it'll come away. You'll now have full access to the machine's innards, like so.

For the trouble I was having, opening up the machine like this allowed me to do a continuity test on the line cord and its reel. That led me to an unambiguous diagnosis of the problem.

Note the following:

a) The on/off switch is not the power switch for the motor -- it's merely a signalling switch that triggers a solid-state switch.

b) The solid-state motor current switch is embedded in the motor -- it's not a discrete component that's accessible for test or replacement.

c) The circuit board is for motor speed control and, presumably, over-heat detection/shut-off.

Re-assembly Note:

There's a peculiar-looking white flexible shaft associated with the motor speed control knob in the foot switch cap. When reinstalling the foot switch cap, you'll have to take care to guide that shaft so it mates with a potentiometer on the circuit board. Aside from that little detail, re-assembly is reasonably straightforward.

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