Dc motor controller is in use, can appear sometimes speed is not normal. What to do about it? The below small make up to introduce. The cause of dc motor controller: it is a high speed; Second, the speed is too low. So can take maintenance methods are: 1. Inspection on power supply voltage, to see if excessive; The main magnetic field is weak, the load of the motor is low; 2. Inspection on the armature winding, look have appeared such as open circuit, short circuit, grounding fault; 3. Check the pressure of brush and brush position and see whether it is right; 4. Inspection on the power supply voltage, to see if too low, and whether the heavy load. The above is with the introduction of the dc motor speed controller is not normal, I hope it can help you.