How to test brushed motor rotor coils with a multimeter?
Rotor brushes are on opposite sides so, look for something ~&lt; 1 Ω on armature contacts in pairs from opposite sides , and continue all around.

Also check the stator windings from the main plug in the ON position or some other convenient method.

Then look under the switch panel for a triac and fixed resistors and look for evidence of burn marks.

Is this a design question?