Many treadmills have been equipped with a slide pot over the years. When you have a treadmill like this, you simply move a little plastic knob straight in a line in order to get the speed to change or to set the speed. The problem is these pots corrode easily and then start having serious speed variation issues.
What we suggest is to replace a slide pot with a rotary pot on any console. They are an exact replacement in terms of controlling speed and are much less prone to failure.
To replace, you would remove the old slide pot from the console, then drill a single hole in the plastic of the console where you want the speed control. The hole needs to be large enough for the stem of the rotary pot to freely insert through and use daily.
A nut is included with the rotary pot in order to snug up the rotary pot to the console face. Once the pot is set, strip the red, black and white wires on the pot in order to twist the wires with the matching red, black and white wires from the original slide pot. When you twist the wires together, use either an insulated nut or electrical tape to cover the wires so they do not hit either a metal part of the frame or another wire.Set the knob on the rotary pot on the face side of the console and then secure the console in place and you are ready to use the treadmill.