need to flip side and with a wrench 1 / 2 or 9 / 16 loosen the screw of motor base and try to press the down key and if so work you should Lift motor replacement
Replacement Parts for Fitness Exercise Equipment at SPORTSMITH
The following link is to a manual for your model. This should provide some insight before disassembling the unit. The most important part is to label the connection wires so that you are sure where they go when you put it back together. Also be considerate of any pinch points so that you do not accidentally pinch or crimp any wires when putting it back together.
249920 NORDICTRACK 1500 TREADMILL SPORTSMITH net