BENDIX ET-2 ELECTRONIC THROTTLE Manual - Page 5

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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.