February 9, 2017 
Hi Paul! My Bosch Maxx9 washing-machine (2yrs old) has a problem I can’t diagnose. The belt OCCASIONALLY slips around rear drum-pulley causing high-pitched squeal, especially when attempting high-speed spin. Runs perfectly sometimes, other times it squeals like crazy. If the drum fails to turn properly for loo long, tacho-sensor ends programme. Similar to unbalanced load, but this occurs even with EMPTY machine. I’m experienced repairing my own washing machines (elements, bearings, timers…) With back removed: belt appears to have inadequate traction around the large drum-pulley. Belt is as tight as you would expect it to be. Replaced belt – same problem. Drain/trap all clear. Pump fine. Water empties completely. Motor spins freely/fast/quiet with belt removed. Drum spins freely/fast/quiet by hand. No play in drum. Tested wiring harness connections to motor (assuming high-speed connection dodgy). All OK. Motor is brushless. 1st guess: Small obstruction between inner/outer drums causing enough traction for belt to slip? Can’t find anything. No bras in household! 2nd guess: Pressure sensor intermittently failing, so machine thinks its full of water? Causing a Go/No-go frequency which jolts the belt? 3rd guess: PCB failure? It’s the intermittent nature of the problem that’s stumping me. It can run fine for days, then squealing belt occurs again. I’ll buy you a CRATE of beer if we can solve this one! 🙂 Thanks,
Alan
Paul answers
Hi Alan!
I have come across this before, on this occasion it was a small sock That was jammed in the Gap at the front by the door seal it was not visible but with a bore scope I was able to see it and using a metal coat hanger I was able to hook it out and remove it.
Cheap Borescopes for mobile phones and tablets
There are some videos below to show you how a borescope works and also other useful videos on Bosch washing machines
if this helps i look forward to a good weekend with the beer lol
Common questions people ask about on Bosch washing machines.
Bosch washing machine Won´t Drain, Will not drain, doesn´t drain, does not empty – these are all pump problems, see video on this.
Bosch washing machine Will not start, won’t start, Will not open – this is usually due to the machine still having water in it or a door interlock fault, see video on this.
Bosch washing machine Will not spin, Wont spin, will not spin, doesn´t spin, fills up but the drum is not turning, won’t agitate or spin – drum doesn’t move!- these faults can either be motor related or pump related
Bosch washing machine Does not take conditioner, is not taking in any water.- these are all water valve related, see videos on this.
If you need any further assistance please feel free to contact me. all the best Paul.
Paul Charmbury
Appliances Engineer
Useful videos on all Bosch washing machine repairs
