HI ! My VMC-15 did an odd thing tonight. The spindle just took it's sweet time winding down without braking . The message is--EMERGENCY STOP-TAKE APPROPRIATE ACTION SPINDLE WOULD NOT STOP
Is the therm-resistor thing usually the culprit in this case? how do you check it ?
Thanks !

The spindle control is MTB dependant, many will drop all power when an emergency stop is issued, this does not allow a controlled stop of the spindle through the Sp Drive, so the motor just coasts to a stop.
The thermal dectection is usually a thermal switch buried in the Motor windings or case and should normally read a closed condition, it will open circuit when exposed to a certain heat level.
A resistance meter with confirm the status.
Al.

is it just a matter of pulling the spindle motor cover off and checking the wires with a multimeter. Or is there a way to test it from inside the elecrical panels?

I am not that familiar with that particular machine, but commonly by taking the spindle cover off , you should be able to identify two small wires that hopefully are marked, if you have the schematics it should help.
The motor may have MS/Cannon connectors, in that case you will need to identify the pins.
Use a multimeter ohms range to check.
They probabally come back to the panel, this is where you need the machine prints.
Al.

I pulled the cover off the motor, was pretty dirty but the fan was running fine. I see what I think is the encoder on top but that is the only wire aside from the fan that I see coming out. I disconnected the regen resistor- 13ohm 1100 watt. I checked it for continuity but got nothing. I think it must be burned out, unless I am not using the multimeter correctly, I am a machinist not an electrician.

Its a pretty straight forward test, at 13 ohms it will read low on any resistance scale.
At 1.1kw the resistor should show signs of over heat or a possible fused open point on the body if it has blown.
Make sure the meter leads have a good connection on the terminals.
Al.

I had a similar experience with a 15Xt. We called uptimecnc.com
they were great, helpful, fixed over the phone and no charge. Just did'nt remember what the issue was. It had nothing to do with a dirty cover though.

It was the Regenerative resistor, I checked it and zero continuity and nothing showed for ohms which should have been 13 ohms. Will order a new one from Uptimecnc or Fadalcnc.

I think it was the choke (regen). Good luck