If your problem was solved with my suggestion. you must replace that thermal resistor or you might burn your motor by operating with a jumper on it. you loose thermal protection for you motor by operating without it or by putting a jumper on it
I know this is an old thread but I just want to help those Dremel owners who might have the same problem on this discussion. try putting a jumper wire on the thermal resistor. one terminal is connected to the carbon contact , the other to the motor windings. its very visible on the second...