Lull 6K Service Manual - Manual (Page 565)

Transmission
Service Manual — Models 644B, 6K, 844C, 8K, 1044C, 10K 8-17
2. Measure forward voltage by connecting the black DMM lead to the
cathode side of the diode and the red DMM to the anode side of the
diode. Typically the value registered on the DMM display will be 0.5V
for a P21787 diode.
3. Measure reverse voltage by connecting the black DMM lead to the
anode side of the diode and the red DMM lead to the cathode side of
the diode. The DMM display should register “OL” for overrange.
4. If both readings indicated “OL”, then the diode is open and should be
replaced.
5. If both readings indicated continuity or 0.0 volts, then the diode is
shorted and should be replaced.
Park Brake Pressure Switch
Description
The park brake pressure switch is a double pole, single throw, normally
closed, 100 psi pressure switch. (Double pole means that there are two
microswitches in the pressure switch.) The pressure switch is connected to
the park brake hydraulic circuit between the park brake valve and the park
brake cylinder. When hydraulic pressure releases the park brake, the
pressure switch senses pressure greater than 100 psi and the switch
opens.
When hydraulic pressure is released from the park brake cylinder a spring
in the cylinder applies the brake. The pressure sensed by the park brake
pressure switch drops below 100 psi and the pressure switch closes.
Machines w/ DW-2
Shifter For machines equipped with a DW-2 shifter, the closed pressure switch
(pressure less than 100 psi and park brake ON) causes one microswitch to
complete a circuit that lights the park brake indicator lamp. The other
microswitch completes a circuit that enables the EST-19 microprocessor to
stop signals to the transmission solenoids that engage forward/reverse
and this declutches the transmission.
Machines w/ DW-3
Shifter For machines equipped with a DW-3 shifter, the closed pressure switch
(pressure less than 100 psi and park brake ON) causes one microswitch to
complete a circuit that lights the park brake indicator lamp. The other
microswitch completes a circuit that sends an electric signal to the
transmission declutch relay. The relay energizes and stops power to the
DW-3 shifter. This prevents the shifter from sending signals to the
transmission solenoids that engage forward/reverse and this declutches
the transmission.
When hydraulic pressure at the switch exceeds 100 psi (park brake OFF),
both microswitches in the pressure switch must open and remain open as
long as the pressure stays above 100 psi. When the pressure drops below
100 psi, both microswitches must close.
Simply put, when the park brake is ON the pressure switch is closed, and
when the park brake is OFF the pressure switch is open.