Help to check electric motor

[ss]

On a Vax vacuum, made a burning smell, switched off tried again later after cleaning filters, burning smell again but still working. When I last switched off it made a sort of screeching noise when coming to a stop. I have taken the motor out and the brushes are ok. The fan part spins freely but also has a rough feel to it like it needs oiled.

Anyhow bottom line is before I bin it could someone guide me to check if the motor is shot or not, I have access to a multi meter if necessary but would need guidance as I only use that for mains testing.

Any other suggestions for checking would be welcome. Oh! and the vax is about 30 years old. (Vax 121)

[harry]

Most electrical faults on a commutator type motor are betrayed by excessive sparking at the brushes. If ignored the commutator is "burned up" making a horrible noise.

Check brushes are free to move in their boxes.

But sounds to me like the bearings are shot/need lubricating. Ball bearing greases. Plain bearings oil. If they are plain and run dry they are quickly destroyed & oil is only a temporary solution. They are often sintered and the sintering is destroyed by dry running.

Make sure the fan(s) are not binding on anything, ie motor spins freely.

[cl]

Heavy sparking with no other particular mechanical problem is usually down to a shorted turn somewhere. That often causes rough running as well as overheating because of the pulsating torque. It will certainly produce 'a burning smell' quite quickly.

[Brian Gaff]

I have a Vax with a low powered motor compared to when it was new. Once again it seems to be ok, just not got the oomph it used to have. Its not mega old but I guess they just do not make motors like they used to these days. Brian

[harry]

Most times, this problem can be cured by a new bag/filter. They get clogged.

Sometimes they can be washed, but this is usually not a permanent solution.