My Sebo X4 will not raise or lower. This is what I did to discover the fault.
1/ Checked that brush was working and not worn down (can stop the raise / lower function). It was very worn, so was replaced. Didn't cure the fault!
2/ Checked power supply to the main PCB board. Yes 18 volts were getting there.
3/ Stripped down the motor / gearbox which raises and lowers the machine. Gears and brushes fine and the motor was checked on 18 volts DC again this worked fine. So reassembled and reinstalled them.
4/ Checked that the small magnet was in place in what people call the clutch assembly. Yes it was there.
5/ Checked to see if a pulse train was being outputed from the magnetic sensor mounted on the end of the main PCB. No there wasn't.
6/ Checked the DC supply to the Hall effect sensor. There was no zero volts on pin 2 and 18 volts on pin 1!!!! Very carefully checked the tracks on the PCB board and found that a groove had been worn in the edge of the PCB where the zero volt line was. Hence disconnecting the supply to the Hall effect sensor. The groove appears to have been worn into the PCB by some foreign object being picked up on the edge of the "clutch" and wearing the PCB until the earth track was severed.
7/ Soldered in a connection from Pin2 to an earth (zero volts point). Checked that the bit of the "clutch" that had done the damage was now clear of contamination.
8/ Reassembled the X4 and all worked as it should.
The moral of this tale is that you should not suspect the motor / gearbox giving a fault condition straight off. If I had used my eyes, I should have spotted the grinding on the PCB more or less straightaway and saved myself a fair bit of time!