Precor Error Code 21 Too Many Maximum Consecutive Power Requests

Feb 21, 2022

Applies to Consumer treadmills, Commercial treadmills pre-2006

Issue symptoms

This error monitors the treadmill's power bit reading when the treadmill operates at speeds above 1 MPH. Power bits indicate the relative time the motor controller drive circuit is switched on. Therefore, power bits is an indication of the amount of power the load is demanding from the motor controller. Error 21 indicates that at a speed of greater than 1 MPH, the motor controller is demanding an excessive amount of power.

The main cause of this error being displayed while the commercial treadmill is being used between 7 and 8 MPH is a missing jumper on a recently replaced LPCA. The next most likely cause is a badly worn running belt/deck. This error can also be caused by badly worn motor brushes, or brushes that are not contacting the commutator. Least likely but possible is a shorted drive motor.

Troubleshooting steps

1. Because the LPCA for the commercial treadmills is the same for both the 120 VAC and 230 VAC, there is a jumper that must be installed on the 120 VAC treadmill. If the LPCA requires the 120 VAC voltage doubler jumper and the jumper is not installed, the treadmill will typically display an Error 21 between 7 and 8 MPH. To correct this problem, install the lower PCA voltage doubler jumper.

WARNING:  Be sure the treadmill is a 120 VAC model before installing the jumper. Installing the voltage doubler jumper on a 230 VAC model will cause the lower PCA to fail.

2. WARNING: Be sure the treadmill is a 120 VAC unit before installing the jumper. Installing the voltage doubler jumper on a 230 VAC treadmill will cause the lower PCA to fail spectacularly.
3. A clamp-on AC ammeter must be used to determine the amount of AC input current being drawn by the treadmill under no load and loaded conditions. Remember, many running beds are double-sided and the bed can be flipped over rather than being replaced. If the current is excessively high at slow speed, replace the belt and deck surface with new.
4. Switch OFF the treadmill and disconnect power from the wall receptacle. Remove and inspect the motor brushes for arcing and pitting. If present, replace both drive motor brushes. Also, check that the brush can move smoothly in the grooves, and that the spring is able to press the brushes against the commutator. Adjust or replace the brushes as necessary.
5. Test the drive motor resistance; it should not be near 0 Ω. If 0 Ω, a known good drive motor must be substituted for the existing drive motor.