I need a new endcap for apex 4100i nttl 18906

Just completed this project. First of all, there are NO screws to remove. Smack in the middle of the endcap slightly below midline there is a rectangle in "portrait orientation" with a tab in it. Reach in and gently pull tab forward while pulling entire assembly upward and it will pop off. Pull the assembly forward and the perpendicular connecting piece will roll forward as well. At a certain point, the end of the pependicular piece (the one attached to the back of the frig) will pop out as it is just wedged into a small vertical notch in the back wall. Take the entire assembly out of the frig and close the door because i promise you that the door is beeping you and the temp has risen to almost 50 degrees. to remove the sliding portion, you need to depress the remaining two tabs from behind to release the sliding portion and gently squeeze the two tabs on the end of the end cap so that you can separate the two pieces. Go slowly as these pieces are flimsy and fragile. You will have to rotate pieces at the back and front of the endcap to get the pieces out that you need to put back on the new endcap. The drawer slide comes out by depressing the remaining tab (just left of the tab that released the assembly to begin with.). Once you have the new "L" shaped assembly, you are ready to put it in. Start with fitting the back piece back into the tab at the rear of the frig. Fit the assembly into the corner, hold the original tab down and it will snap into place easily. Putting the cover back into place is a bit tricky, you will have to stick the hole of one side od the cover first and then gently pull back the tab on the other side to accommodate the other side hole. I was super careful because I didn't want to break the cover tab that made me have to change the end cabin the first place.

Try the calibration procedure found in the troubleshooting section of your manual first. Here are the basic instructions.
With the key in the console, press one of the Incline buttons. While the incline is changing (or the numbers on the console) , remove the key. After a few seconds, re-insert the key. The treadmill will automatically rise to the maximum incline level and then return to the minimum level. This will recalibrate the incline.
If it still doesn't move, remove the cover. Find the incline motor. You will see a slot in the end of the motor. Using a drill with a standard slotted screwdriver bit, spin the motor counterclockwise (if it is having difficulties spinning, turn clockwise instead) for just a couple seconds. Now do the calibration procedure again.
I have had machines that got stuck before. Once released and recalibrated, the operation was OK.
The service number for your machine is found on the model number sticker on the frame of the treadmill.

Sorry to inform you, that part is no longer available from the manufacturer.

Have you got in touch with the company that makes them?

You can try and do a re-calibration on the treadmill (Its listed in the Users Manual) but it sounds like the console has gone bad. To repair this you would have to replace the entire console.

hold down stop and speed + then put safety key on
hit stop once
push incline+
let it go up and down
take key off and reattach
try
if it still doesn't go the incline motor is bad

You can purchase this item at iconfitness.com go to customer service click on to part replacement parts input manufacturer then model name it pop up 17 matches, but they all use the same diagram number and that is number 105, part number is 151071 price $11.81 each

You need to have the power supply board rebuilt with larger Caps and resistors. Look on the internet under treadmill repairs. The board is easy to replace yourself so don't have someone come in and overcharge you. I think about 4 screws and two plugs.

try caibrating it.

Go to Nordiactrac.com and enter your Model number from the sticker on the frame. It should read NTL or NTTL then 4 or 5 number. Folow the instructions and ask for the Part's List. You should be able to find it there.