Troubleshooting
20
3A1185B
Sensor
Plug another sensor board into the board and
perform the zero calibration procedure. If the
machine starts to run, the sensor is bad. If
there is no replacement sensor available, use
a multi-meter to test the resistance across the
red and black wires of the sensor (be sure to
test the plug). You should read 1.5 - 3.5k
ohms. A faulty sensor usually reads no conti-
nuity (open).
If the sensor passes all the tests, see Pres-
sure Control Knob (Potentiometer).
Pressure Control Knob (Poten-
tiometer)
Plug another potentiometer (POT) into the
control board. If the machine starts, the old
POT is bad.
When a replacement POT is not available,
remove the POT lead (with the machine
turned off) from the control board and test the
resistance between the red and black wires
(be sure to test at the plug). The resistance
should read between 8-12k ohms. If it is out-
side of this range replace the POT.
If there is DC voltage at the motor brushes
and the sensor and pressure control knob are
functioning, replace the pressure control
assembly.
Problem
Cause
Solution
