What causes a landice treadmill to start then stop then start and stop then shut down on overspeed

An OS or O5 error on the Landice L-Series treadmills, such as the L7, L8 and L9, indicates an over speed condition and this occurs when the actual speed of the running belt is faster than the set speed. The possible causes for an overspeed, OS or O5, error are: A) User weight is over 200lbs, treadmill elevation is set between 10% and 15% grade and speed is set between .5 mph and 3 mph
B) User is pushing against treadmill belt causing it to go faster than the set speed
C) Defective lower board or misaligned speed sensor
D) Maladjusted speed potentiometer

Corrective Action

A) Gravitational force will enable the user's weight to move the treadbelt faster than the set speed. The speed sensor will pick up this increase in flywheel speed and sends this information up to the display electronics. The microprocessor will then compare the actual speed to the displayed speed, determine a runaway speed condition and shut the treadmill down. An overspeed will display in the window. This is a safety feature built into all treadmills that utilize closed loop speed circuitry. The way to address an over speed condition due to gravity is have the user decrease elevation below 10% or increase the speed.

B) Similar to the gravitational force, a user can be holding onto the handrails and pushing the running belt in such a manner where they are using the treadmill like a manual machine rather than a motorized one. User needs to set speed compatible for their actual walking or jogging speed so they are not pushing the belt.

C) It's possible a blown motor control board is the problem. This occurs more frequently with PWM drives than SCR drives. However, this problem is becoming rare due to the PWM circuitry which senses this condition and shuts itself down before the drive motor receives any DC voltage at all. This means you'll get an LS or L5 error if your PWM is blown, not an OS or O5 error. This is a safety feature on all Landice home treadmills with PWM motor control boards. The SCR motor control boards also have internal protection to prevent an over speed condition from occuring due to an internal component failure. In the rarest of cases, on home treadmills, a faulty relay board can cause an OS or O5. To verify this, using a digital voltmeter, with treadmill turned on, measure the DC voltage between the V+ and P1 on the PWM board. The reading should be between 6-7 VDC. Also measure the DC voltage between P1 and P2 on the PWM board. The reading should be between 0.5 VDC and 6-7 VDC. If either of these voltages measure zero, replace the relay board.

D) Get into Open Loop Speed mode and check the speed. Adjust pots as necessary to bring up correct speed for max and min.