This error is present on treadmills using an SCR motor controller and the C544 EFX. Because
the treadmill running belt speed (and C544 resistance) is derived from the A.C. line frequency, it
is critical that the unit’s operating system can correctly identify the A.C. line as either 50 Hz. or 60
Hz. and ensure that the line frequency is within acceptable tolerances.
1. The treadmill is operating on a non-dedicated A.C. circuit.
2. On 120 V.A.C. circuits the A.C. hot and A.C. neutral wires are reversed.
3. Incorrect jumper setting on the upper PCA
4. The fuse feeding the treadmills stepdown transformer is blown.
5. The A.C. line frequency is incorrect.
6. The A.C. line may be extremely noisy.
1. Treadmills must be installed on a completely dedicated 20 amp A.C. circuit. Both the hot and
neutral leads must be dedicated to the treadmill. If another piece of equipment is sharing a
circuit with the treadmill it can create enough electrical noise to make A.C. line frequency
identification impossible. The treadmill’s A.C. circuit must be reconfigured as a completely
dedicated 20 amp circuit.
2. Most line frequency detection systems monitor the A.C. line frequency on the hot A.C. line. In
the case of a reversed 120 V.A.C circuit, the monitoring is taking place on the neutral
(ground) side of the A.C. line. Many of the monitoring systems are incapable of detecting line
frequency on the neutral wire. It must first be determined if the reversal is in the A.C. wiring
feeding the treadmill or in the treadmill internal wiring. The hot and neutral wires can be
verified by measuring each in reference to A.C. (green wire) ground. The hot lead will read
full line voltage (typically 105 to 120 V.A.C.) and the neutral line should read approx. 0 V.A.C.
3. Some upper PCA’s had jumper setting for use with “SCR” or “PWM” drive circuits. If the
upper PCA jumper was set for “PWM” operation on an SCR unit, error 10 would be displayed.
Change the upper PCA jumper setting to “PWM” to correct the problem.
4. Some treadmills (C944 PWM version 2 and C96X PWM version 2) utilized a pair of fuses
feeding the stepdown transformer for the low voltage power supply on the lower PCA. The
A.C. line frequency was monitored on the output of one of the fuses. If the fuse blew, A.C.
line frequency could no longer be detected even though the treadmill appeared normal
5. Even though unlikely, the A.C. line frequency could actually be out of acceptable limits. This
is more likely to occur in countries where A.C. power systems may not be well developed and
controlled. There may be little that can be done about this condition. If the source frequency
can not be corrected the only possibility may be replacing the treadmill with a treadmill
utilizing a PWM motor controller. PWM motor controllers do not depend on line frequency for
6. Sometimes A.C. being fed into the distribution system is too electrically noisy to allow correct
line frequency identification. This can be caused by other equipment within the A.C.
distribution system creating the electrical noise. Identifying the source of the electrical noise
can be difficult. There may be little that can be done about this condition. If the source can not
be located or the source can not be removed or made electrically quiet the only possibility
may be replacing the treadmill with a treadmill utilizing a PWM motor controller. PWM motorcontrollers do not depend on line frequency for speed control.