Power Soak 34773 ps-200/201 Service Manual - Manual (Page 10)

7
Component Operation and Checks
The following checks should only be performed by qualified
technicians using extreme caution. Electrical hazard to
untrained personnel may result in electrical shock, burns, or
death.
Liquid Level Sensors
There are two Liquid Level Sensors (LLS) in the wash sink, and two more in the sanitize
sink (if equipped with a sanitize sink). To check operation, first unplug the white
connector from the UPM. Using and Ohm meter, measure the resistance between the face
of the LLS and the appropriate pin of the white connector. The meter should read less than
one ohm. Refer to the chart below for the appropriate pins.
Description UPM pin number Wire Color
Wash Sink Low LLS Pin 19 White with Orange stripe
Wash Sink High LLS Pin 20 White with Green stripe
Sanitize Sink Low LLS Pin 21 White with Yellow stripe
Sanitize Sink High LLS Pin 22 White with Blue stripe
If the meter shows a reading higher than one Ohm, there may be a dirty sensor, a broken
wire, or a loose connection. The loose connection may be at the sensor, the wiring harness,
or the external wiring harness may not be tight at the back of the Control Panel.
Thermistor
The Thermistor is a temperature sensor. The UPM measures the resistance through the
Thermistor, and associates that resistance to a temperature. To check operation, first
unplug the white connector from the UPM. Next, measure the resistance across the
Thermistor. This reading can be attained at the white UPM connector (reference “UPM” for
pin layout), between pin 8 and pin 9. If the reading varies significantly from the
Temperature-Resistance chart in Appendix A, the Thermistor may be defective. The UPM
will signal an error if it reads a resistance greater than 430 kΩ and less than 15kΩ. The
Thermistor is located close to the Heater, inside the Sensor Pad. When replacing a
Thermistor, it is helpful to use a glue dot to hold it in place while reattaching the Sensor
Pad to the sink. Also, it is imperative to put heat sink compound on the side of the
Thermistor that will be against the sink, and the Heater Thermodisc as well, to help ensure
good heat transfer.