PowerMax upright or canister?
If canister, I imagine it's the suction unit you're talking about. The canister suction unit does get fairly warm on base of unit after a few minutes of use. The canister suction unit is equipped with a rheostat which would shut the unit off if it was excessively hot.
Canister versions of the PowerMax series had various motor sizes over the years. Total amperage for machine stickers have changed from 10.5 Amps to 9.8 Amps, 9.6 Amp units and 9.3 Amp units.
Some things to check for the canister:
-- Bag installed propertly. HEPA or similar filtration bag is preferable. Honeywell brand vacuum bags do not perform well in these units.
-- Clean and white pre and post motor filters. Post Motor filter is under the dusting brush.
No hose or wand blockage. Remove hose and see if airflow is dramatically stronger and if unit runs as hot with hose removed. --- Allow unit to cool and then run with hose removed to test this theory.
Check wiring in housing area. Ensure no wires are heavily tangled, showing signs of wear or possibly getting loose.
If machine was ever run without a bag or filter not installed properly then there may be dirt in the motor. The fan housing may need to be taken apart and cleaned. In process of doing that, then upper and lower bearings should get greased.
PowerMax upright-- older style with cloth bag, would be a tougher unit to repair. There are several parts to disassemble to get to the motor. Bearings probably need greased for that model if the case, and check fan housing.