This condition is when the treadmill goes to full speed as soon as you power up the treadmill. Typically when this occurs, it is an indication of a short circuit in the motor controller. To test to make sure the problem is in the motor controller, perform the following steps (this test only works on treadmills with simple SCR controllers like a MC-60...if you have a digital treadmill or a more complex treadmill skip to the second test section):
First Test Section
1) Unplug the treadmill from the wall.

2) Remove the motor hood.

3) Unplug the speed wires from the controller. On many controllers, you will have 2 to 3 wires that control speed and many are labeled H, W, and L. If you cannot find the speed wires, do not guess, contact us with your make and model number and we will try to help you with the wiring.
4) Return the treadmill to a usable position once the speed wires are disconnected and plug the treadmill back in.

5) If the treadmill begins to run at full speed, the motor control has failed and requires replacement.
6) If the treadmill does not run at full speed you could have a speed input problem, wiring problem, or another short circuit.
Second Test Section
1. Unplug your treadmill from the wall.
2. Remove the motor hood.
3. Check and see if your controller has three speed wires labeled H, W, and L or a unified wiring harness labeled H, W, and L from the console. If not, you have a digital controller and full speed upon power up is always a failed controller. No need for further testing...you need to replace the controller.