Precor Treadmill C956 error 21

Precor Error Code 21 Error Code: 21 Manufacturer: Precor
Model: All Models
Error Description: Error 21, Too many Consecutive Power Requests- The error 21 observes a treadmill's power bit reading when the treadmill was operating at speeds above 1 mph. Power bits indicate the relative time that the motor controller drive circuit is turned on. 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 greater than 1 mph, an excessive amount of power is being demanded from the motor controller. Possible Reason:

1. A badly worn deck and/or running belt can cause the error to appear when the unit is in use.
2. Badly worn drive motor brushes may not be making proper contact with the drive motor commutator causing the error to occur when the unit is in use. The unit may also slow down or become sluggish when the load or speed is increased.
3. A jumper may be required on the lower PCA if installed into a 120 VAC (Version 2) treadmill.
4. A leaky or shorted drive motor filter capacitor (on units equipped with SCR motor controller) could increase the current demand enough to cause the error.
5. A leaky or shorted drive motor inductor (on units equipped with SCR motor controller) could increase the current demand enough to cause the error.
6. The high power demand is caused by a shorted or de-magnetized drive motor.

1. Determine the amount of AC input current being drawn by the unit under no load and loaded conditions using a clamp on AC ammeter. The current displayed can be used to determine the condition of the deck and/or running belt. These same readings should be taken on a like unit, in good operating condition with a know good deck and running belt. The readings from the unit in good operationg condition can be used as the benchmark. Compare readings and replace* the deck and/or running belt if necessary. *Some units have a reversible deck. Be sure if the deck is being flipped or replaced, a new belt is installed on the new deck surface.*
2. Inspect and repalce both drive motor brushes if necessary.
3. Inspect the lower PCA (if unit is 120 VAC/ Version 2) for jumper. If jumper is not installed, error typically appears between 7 mph & 8 mph. Install jumper if necessary. CAUTION - DO NOT install jumper if unit is 240 VAC. Installing the jumper on a 240 VAC unit will casue the lower PCA to fail.
4. Measure the AC input current without a load using a clamp on AC ammeter. Electrically isolate the filter capacitor from the drive motor circuit. The drive motor leads need be kept intact so the drive motor will operate with the filter capacitor removed from the circuit. Re-measure the no load AC input. If the AC input current is significantly lower, replace the filter capacitor.
5. Measure the AC input current without a load using a clamp on AC ammeter. Electrically isolate the inductor from the drive motor circuit. The drive motor leads need be kept intact so the drive motor will operate with the inductor removed from the circuit. Re-measure the no load AC input. If the AC input current is significantly lower, replace the inductor.
6. Swap the existing drive motor with a known good drive motor.