My Vision Fitness T9450 is having a power issue. I plug it in, turn on the power button in the back, the console lights up as normal. Then when I press start the power goes out before the belt even st

Question edited for clarity.
Question moved from Cars and Trucks to model category.

It can only be the speed sensor or the main control board or the connections to it. Remove them and clean with electrical contact cleaner.

https://www.google.com/search?q=vision+fitness+T9450+no+speed+control

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First thing to do with these folding vision fitness treadmills is
REPLACE THE MAINS SUPPLY CABLE
They were supplied with very poor quality cable that cause issues like juddering stopping and speed fluctuations.

If you wish to get some details; check the site linked here. Pull up older posts. http://electro-medical.blogspot.com/

The primary cause of E5 is the elevation system malfunction - Elevation error (signal lost)
First check all wires from the elevation motor to the lower motor control board. Also check the main wiring harness from the console to the lower motor controller to determine if a wire has been cut, pinched or shorted to ground.

If all wiring is in perfect condition and the unit has not been recently moved, dismantled/reassembled, then there might be a failure of the lift motor itself, or in some cases the motor control board (controller)

It sounds like you have a membrane issue. There are a number of different T9450 models and they all have slightly different consoles. You'll need your serial number to help pinpoint the parts you need. Your best bet is to go through the manufacturer (johnsonfit.com) and have them help you get the correct membrane and overlay.

look at your manual for the blow out picture remove the rite screws and have some one help you hold the console while you disconnect the wire harness

Take the front cover off and see if the drive belt is on the motor. Try running it to see if the motor turns. This could be a motor or controller board problem.

safety switch could be defective

First Your outlet to see if power is their, then check on/off switch usually their is an internal light in the switch to show power is to the switch then check the breaker button next power switch. these are a few things to look at. Check if the safety key in place on the upper console