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Closed Throttle (open) Range: 10-20%
Open Throttle (full) Range: 75-90%
PEDAL
POSITION
SENSOR
(PWM)
.001µF
™
FIGURE 8 - ET-S
TREADLE ELECTRICAL TEST SCHEMATIC FOR THE CATERPILLAR CONNECTOR
potentiometer until the ohmmeter reads the same
resistance as shown on the label within ±10 Ohms. Next,
while holding the potentiometer at the set resistance
screw and lock the potentiometer in place (torque to 25
inch pounds ±5). The sleeves lock into the body of the
potentiometer for easy removal and reassembly.
Test 2: Where the potentiometer has no label, but
has engraved set voltage shown. The Cummins
potentiometer on the ET-2
validation switch. It also has a set voltage value marked
on the cover, which needs to be used to properly install
the potentiometer. The drive slot in the potentiometer should
engage with the drive tang at the end of the drive shaft.
Next rotate the potentiometer until the hole in the metal
sleeve matches the mounting holes on the actuator base.
Loosely screw the potentiometer in place but do not
tighten. Construct the test circuit following the circuit
diagram shown in Figure 8. To make the test circuit
connect the test load resistor (47,000 Ohms) and a
capacitor (.01 Microfarads) across pins 3 and 4 of the
potentiometer. Then connect a voltmeter to the lead ends
of the test circuit. Next connect a 5 volt power supply to
the potentiometer at pin 4 (APS ground) and pin 5 (supply
voltage). Caution: Sensor may be damaged if supply
exceeds 5 volts. Now the installer should read the set
voltage value marked on the potentiometer. Rotate the
potentiometer until the voltmeter reads the same voltage
as shown on the potentiometer within ±.02 volts. Next
PIN A VREF
(INPUT)
-8V
2000 OHM ±5%
RESISTOR
PIN B
VOUT
(OUTPUT)
RED
47,000 OHM ±5%
RESISTOR
PIN C
VOLTMETER (V => %)
GROUND
BLACK
Caterpillar output voltage is Pulse Width Modulated
™
treadle has an integral idle
(CABLE)
screw and lock the potentiometer in place (torque to 25
inch pounds ±5). The sleeves lock into the body of the
potentiometer for easy removal and reassembly.
Test 4: For CAT engines:
1. Securely clamp the treadle Mounting Plate (6).
2. For Caterpillar Potentiometers: Aligning the drive slot,
the Potentiometer (1) engages the drive tang at the end
of the Cam Follower Drive Shaft (see Figure 4). Rotate
the Potentiometer clockwise until the first set of
mounting holes align. Secure using two screws (2):
torque to 20 (±2) in. lbs.
To test the Caterpillar sensor construct the test circuit
shown in Figure 7. Connect both pin B and pin C into
a voltmeter. Set the voltmeter to the settings described
in Figure 7. Record the output values in Figure 2. If
the unit does not operate within the specified ranges,
service the unit or replace it with a new ET-2
REMOVAL
1. Park the vehicle on a level surface and block the wheels
and/or hold the vehicle by means other than the air
brakes.
2. Drain the air pressure from all vehicle reservoirs.
3. Unplug the cable assembly at the opposite end of the
potentiometer. Disconnect by lifting the lock tab and
pulling the connectors until they disengage.
4. Remove the ET-2
™
treadle from the vehicle.
POTENTIOMETER
™
treadle.
5
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