Hey there, sorry to hear you're having an issue with your elevation motor. I would be happy to help you solve the problem.
Since you already installed your motor you can go straight into diagnostic mode.
To get into Diagnostic Mode on your L8
Make sure to turn off your treadmill.
-ET's - Press Menu and Start at the same time
-CT's - Press Manual (or Display^) and Start at the same time
-All other L SERIES mills - Press Display (or display and Start at the same time
-*CT's that were manufactured after 09/2003 - Press Display and start at the same time.
Few things you want to do, if you haven't already.
A. Align the motor with the clevis mount and install the motor mounting pin.
B. Insert hitch pin.
C. Reconnect the elevation harness to the lower board
D. Set the lowest limit switch by holding the UP elevation button for 5 seconds. Then press and hold the DN elevation button one more time to make sure you only hear a click.
E. For L7/L8 machines; Thread the elevation nut to where its flush with the threads on the "worm' shaft.
F. Mount the elevation nut to the leg assembly by lining up the holes on the leg assembly. You may have to move the leg assembly so that the holes on the elevation nut line up. Then slide the two elevation pins through the elevation assembly and into the elevation nut. then secure the pins with the 2 set screws.
To calibrate your potentiometer you can try to adjust while it is installed but for best results you must calibrate it before its in your motor housing.
G. Calibrate the elevation potentiometer and to do so you must;
1st: Visually confirm treadmill is leveled. (0% grade)
2nd: Adjust the settings as follows;
All L SERIES millls should read 0.0
3rd: If the setting is incorrect, follow these steps.
Step 1: Turn the post of the potentiometer all the way
Step 2: SLOWLY turn the potentiometer COUNTER
CLOCKWISE until the setting is correct.
H. Carefully install potentiometer into the motor housing
*NOTE: The setting may vary when inserting the potentiometer
into the motor. As long as the change is minimal, fine
adjustment can be achieved by rotating the meter
while inside the elevation motor.
I. Press OFF to turn treadmill off. Then restart the machine in manual mode to TEST elevation after resetting your potentiometer. As long as the change is minimal, fine adjustment can be achieved by rotating the potentiometer while inside the elevation motor.
For more Diagnostic features and possibly further detail, I will be attaching a Link to your machines service manual. I hope this helps, always hear to help. SportSmith.