Service Manual User Manual

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.