Thermador range hood ventilaor motor failed

Its better you replaced the running capacitor maybe its faulty already.

Regards:
VOTIT

Hello and welcome to FixYa!,

It sounds like there may be a Power ource, Too High or too Low for the Motor to Handle, Which is Making it burn Out.

Try a different Power Source at a Higher Or Lower Voltage- After replacing the Motor!

Hope this helps --P3NGYJ03

Unclogging the exhaust system Step1Remove the grease filter by sliding it out of its clips.Step.Submerge the filter in a plastic pan filled with hot, soapy water and 1/2 cup (4 fl oz/125 ml) ammonia. Let it soak for at least 15 minutes. If it's still dirty, soak it again, then rinse it thoroughly and set it aside to dry.
Step3Remove the exhaust fan. Unplug the fan, then use a screwdriver or a nut driver and socket to take out the screws that attach it to the hood.Step4Clean the fan blades with an old toothbrush dipped into the ammonia-water mixture (see Warning).Step5Clean the inside of the exhaust ductwork, using a plumber's snake with a heavy rag tied around the end. Push the snake through the ductwork. Soak the rag in the ammonia and water mixture, then run it through the ductwork. Rinse out the rag and repeat the operation until the duct appears to be clean.Step6Clean the exhaust hood that's attached to the outside of your house. Use the old toothbrush and the ammonia-water mixture to loosen the grit and grime around the flapper plate. Make sure the plate moves freely when you're done. If it sticks closed, it can prevent the exhaust hood from working.
Step7Reinstall the grease filter.
Replacing the fan motor Step1
Remove the grease filter by sliding it out of its clips.
Step2
Turn on the fan and inspect the motor. It needs to be replaced if it hums rather than turns, turns very slowly, runs for a short time then stalls, or feels very hot and won't turn.
Step3
Disconnect and remove the fan, following step 3, above.
Step4
Take the fan to an appliance store to get an exact replacement.
Step5
Install the new fan.

Grinding sounds like the rotor in the motor has grounded. And if you've lost the 2nd motor in a month, how long did the first motor last?

Confirm that the unit has 120 VAC, and not 208-240 VAC or something over 120 but no more than 208-240.

If I remember correctly (friend has one), these are 1/3 HP motors, and they are pretty robust. Bumping and rubbing for a month of normal intermittent operation should not have caused premature failure.

Was the motor replaced by a tech, and if so, did he hear the noise after replacing the new motor?
Was motor current measured?
Is there a run capacitor in the electrical panel, and if so, was it replaced when the replacement motor was installed? (You always replace the run cap when replacing the motor!).
Can you twirl the motor by hand, then turn on before it stops turning, and the motor continue to pick up speed and run properly? (If so, replace run capacitor).

I'd start with the motor brushes.

There are many companies that make replacement motors, call a contractor's electrical supply, (check the phone book) they sell to the public, they can supply u with a higher quality motor, just bring the old one with u and they can match it up.

If the motor started making noise, it could have lost grip on the bearing, in this case the motor will be still working.

You need to test the new motor by energizing it. If the motor works reassemple it properly, or test the wirings.

If the motor is stiff then you need to use grease on bearings.

If the motor had blown, then there is need to test the voltage from motor control board, that can be reason why you have blown the two motors.

Usually Putting High Temp Grease On The Fan Motor Shaft Will Do The Trick And Make Them Last A lot Longer.

Check for power in the wiring coming into the hood.

Also check for a loose wire or a defective fuse.