Precor 5.17 - Troubleshooting the Speed Sensor

5.17 Elliptical Fitness Crosstrainer
Page 19
Procedure 5.3 - Troubleshooting the Speed Sensor
Circuit Description
The speed sensor is a reed switch. A magnet is mounted on the step up pulley. The magnet
passes the speed sensor once per revolution. The output from the speed sensor is a 5 Vdc
square wave, the frequency of which indicates the operating speed. When a square wave output
is not being generated from the speed sensor the system assumes the unit is not in use and
disables lift (ramp) operation and resistance level changes.
WARNING
Before continuing with this procedure, review the Warning and Caution statements listed in
Section One, Things You Should Know.
Procedure
1. Remove the rear covers. Set the on/off switch in the “on” position. Operate the unit. If the
system timer has not started and a stride rate is not displayed, the speed sensor is not
operative. We shall use the presence of a stride rate to determine when the speed sensor is
functioning normally.
2. A magnet must be installed in the step up pulley. If the stride rate is not being displayed in
step 1, verify that a magnet is installed in the step up pulley and that the space between the
end of the reed switch and the step up pulley is approximately 1/8 inch (See Diagram 5.2).
Diagram 5.2 - Speed Sensor
3. Rotate the step up pulley so that the speed sensor magnet is not near the reed switch.
Using a DC voltmeter, measure the voltage between terminal 1 and terminal 2 of J2 on the
Step
S
Step Up Pulley
Magnet
Reed Switch