75ZT Community

Do we have any domestic appliance technicians on this forum?

I have a Bosch condensor dryer, that has developed a fault.

When the machine is switched on there is a sound of humming as though an electric motor, (the one that turns the drum?) will not start.

The heating elements work and when the machine is switched on the humming starts, if I give the drum a slight push, it starts to rotate as it should. The belt is intact, the timer and off/on switches are ok.

Does anyone have any ideas?

Cheers

Mike

I would be check ing to see if the brushes on the motor are worn

As Dave says, brushes are a good starting point, though if bad enough to not start, I'm not sure you'd get the humming. Depends on the motor design. Might also be a dead sector in the armature. Does it seem to struggle when it does run?

Hi Duncan,

No once running it is ok, however going through the cycle there are times when it stops and then rotates in the opposite direction. When it stops I get the humming sound and have to give the drum a push for it to start rotating again.

Thanks for you reply.

Mike

Seem to remember some motors require a capacitor to start the motor, could be a similar set up if not the brushes?

I repaired a washing machine the other day (no, I'm not a repair man...) where a capacitor had fallen off it's bracket. The wires had then dangled on the drum and during the heating cycles the wire had slowly melted through thus causing the drum to fail to rotate. I repaired the wire and the capacitor looked well despite it's slightly-melted outer casing. Once strapped back up in place on the bracket the washing machine was back up and running! Symptoms were similar though were some noises were heard but the drum did rotate not

This model does have a capasitor.

I just ran it for 5 minutes and came down stairs to the smell of burning / hot electrics and the drum had stopped. The smell was coming from underneathe the drum and when I rotated it the section that had been underneath was hot.

Seems the motor that turns the drum is kaputt?

takestock wrote:Seem to remember some motors require a capacitor to start the motor, could be a similar set up if not the brushes?

Your quite right, some motors need a capacitor. I've not come across these in domestic appliances, but never say never. They are usually on brushless motors, and they tend to be either industrial, or for places where they are running an awful lot but don't need much power.

On reflection, I seem to remember a washing machine that kind of growled when the brushes went, but I think it still turned, albeit slowly.

Like you said from the Off, though, brushes is the cheap and easy place to start. It's not just cooling fans on 75s!

Rover418275 wrote:This model does have a capasitor.

I just ran it for 5 minutes and came down stairs to the smell of burning / hot electrics and the drum had stopped. The smell was coming from underneathe the drum and when I rotated it the section that had been underneath was hot.

Seems the motor that turns the drum is kaputt?

Thats another problem solved them

Rover418275 wrote:This model does have a capasitor.

I just ran it for 5 minutes and came down stairs to the smell of burning / hot electrics and the drum had stopped. The smell was coming from underneathe the drum and when I rotated it the section that had been underneath was hot.

Seems the motor that turns the drum is kaputt?

Most things have a capacitor, but usually only for interference supression.

If the brushes were on their last legs, they may have now given up. They would be arcing, so would have worn the last bits away very fast. If the motor is still drawing some current, but not turning, it would get hot. Before you condemn the whole motor, check if brushes are available. Have to say I can't find them for dryer motors, but with a model number you might succeed.

Thanks everyone for your help, time to call the repair man.