I have a Eureka Central Vac CV1601b. The motor does not stop unless the Unit is unplug from the electrical outlet. Any Idea?.I removed the control unit to check if there was disconnected wires or burnt wires. Everything look normal. The circuit board does not show area that overheated. There seem to be 2 relays. Likely one of the two went bad. What do you think.

If the unit is relay controlled, there is always the possibility that when the unit was turned on, the relay contacts welded themselves shut making the power button ineffective.

If you're familiar with relay pinouts, with the unit unplugged, verify the contact closures with an ohmmeter or continuity checker. With the unit unplugged, the relay contacts should be in their "normal" state (probably open).

Try gently tapping the relays to see if it can be freed that way. If that works, there's nothing stopping them from welding themselves together again. The relay may need replacement.

Cheers.