Bendix Commercial Vehicle Systems ET-S User Manual
®
Bendix® ET- S™ & ET-S2™ Suspended Electronic Treadle
SD-15-4111
TREADLE
ACTUATOR BODY
MOUNTING
TREADLE
FIGURE 1 - ET-S
PLATE
CONNECTOR
POTENTIOMETER
ET-S™ TREADLE
™
AND ET-S2™ ELECTRONIC TREADLES
ACTUATOR BASE
MOUNTING
PLATE
DESCRIPTION
The ET-S™ and ET-S2™ treadles are engine compartment
bulkhead mounted electronic treadles. On electronically
controlled diesel engines, the electronic treadle fulfills the
same function as a conventional mechanical throttle.
However, rather than transmitting a mechanical force to the
engine governor, the electronic treadle controls engine speed
by supplying a variable electrical voltage to the engine’s
electronic controller.
The main components of the ET-S™ and ET-S2™ treadles
are: a mounting plate, suspended treadle, potentiometer
(variable resistor), actuator body and base. The selected
potentiometer, chosen for a specific engine application,
provides the electrical link to the engine control system.
OPERATION
The electronic treadles provide smooth, graduated throttle
control through the function of its potentiometer (variable
resistor). The drive shaft of the cam follower assembly
transfers any movement of the treadle to the potentiometer.
POTENTIOMETER
MOUNTING
PLATE
TREADLE PIVOT PIN
TREADLE
ET-S2™ TREADLE
DETROIT CATERPILLAR CUMMINS
DIESEL
CLOSED
THROTTLE 7 - 18% 10 - 20% 5 - 17%
IDLE (OPEN)
OPEN
THROTTLE 74 - 90% 75 - 90% 70 - 81%
(FULL)
FIGURE 2 - OUTPUT VOLTAGE, AS A PERCENTAGE OF
SUPPLY VOL TAGE
8V
CATERPILLAR
5V
™
ET-S
TREADLE
OUTPUT
VOLTAGE
○○○○○○○○○○○○○○○○○○○○○○
0V
CLOSED THROTTLE
(OPEN)
FIGURE 3 - OUTPUT VOL TAGE
CUMMINS
DETROIT
DIESEL
OPEN THROTTLE
(FULL)
MAX
RPM
ENGINE
IDLE
1
As the potentiometer rotates, its resistance changes. This
way , the potentiometer can react to the driver’s request for
™
engine power through the ET-S
or ET-S2™ treadle by
changing resistance. The resulting change of voltage is
sensed by the electronic engine controller.
The electronic treadle receives its supply voltage from the
engine control unit. If the driver does not request engine
power, the treadle is in the idle position. This condition is
also referred to as “Closed Throttle.” In this state, the
potentiometer returns the minimum percentage of supply
voltage to the engine control unit (see Figure 2).
As the driver depresses the treadle, the electronic treadle
output voltage increases (see Figure 3). The potentiometer
allows an increased amount of its supply voltage to return to
the engine control unit, which in turn increases the engine’s
speed.
In the full, or “Open Throttle” position, the driver has
depressed the treadle to its furthest possible point. This is
the state of least potentiometer resistance. The electronic
treadle returns the maximum percentage of supply voltage
to the engine control unit (see Figure 2).
PREVENTIVE MAINTENANCE
Important: Review the warranty policy before performing
any intrusive maintenance procedures. An extended warranty
may be voided if intrusive maintenance is performed during
this period.
Because no two vehicles operate under identical conditions,
maintenance intervals will vary. Experience is a valuable guide
in determining the best maintenance interval for a vehicle.
GENERAL
Important: Visually check for physical damage to the
electronic treadle such as broken or missing parts. Actuate
the pedal five times from stop to stop, noting any binding or
soft pedal response.
Important Note: DO NOT DISASSEMBLE THE ACTUA TOR
BODY. Replace the ET-S™ or ET-S2™ treadle if there is
any binding, soft pedal actuation or if the nylon washers or
retaining rings indicated in Figure 4 are cracked or have
signs of deterioration.
CAM FOLLOWER
DRIVE SHAFT
POTENTIOMETER
MOUNTING PLATE
FIGURE 4 - TOP SECTIONAL VIEW
RETAINING
RINGS
NYLON
WASHERS
Perform the inspections presented at the prescribed interval.
If the electronic treadle fails to function as described, it should
be repaired or replaced with a new or genuine Bendix remanufactured unit, available at any authorized parts outlet.
Every 3 months, or 25,000 miles, or 900 operating hours:
1. Remove any accumulated contaminants and visually
inspect the exterior of the electronic treadle assembly
for physical damage or excessive corrosion.
2. Inspect electrical connections and cable assembly for
signs of corrosion, wear, or physical damage. Replace
as necessary.
3. Inspect treadle spring, sleeve bearing, nylon washer,
rubber treadle cover (ET-S™ treadle only) and retaining
ring for cracks or deterioration. Replace as necessary .
ET-S™ & ET-S2™ TREADLE REMOVAL
1. Park the vehicle on a level surface and block the wheels.
2. Drain the air pressure from all vehicle reservoirs.
3. Disconnect the cable assembly of the potentiometer.
Lift the lock tab and pull the connectors until they
disengage.
4. Remove the electronic treadle from the vehicle, set aside
the mounting hardware for reassembly.
DISASSEMBLY
Please note that the internal mechanism of the ET-S™ and
ET-S2™ treadle are not field-serviceable and therefore
individual parts or parts kits are not available for these
components. Disassembly may lead to malfunction of the
ET-S™ or ET-S2™ treadle.
The following instructions cover the maintenance and
replacement of the potentiometer and treadle (with its
bearing, spring etc.) only. The instructions provided with
those items should be followed in lieu of the steps presented
here. There are no other field-serviceable parts.
2
MOUNTING
PLATE
ACTUATOR
BODY
ACTUATOR
BASE 1
TREADLE
ARM
ET-S™ TREADLE
POTENTIOMETER
PIVOT PIN
2
#10 SCREWS
7
SPRING
3
RETAINING
RING
4
NYLON
WASHER
REPLACEABLE
RUBBER
COVER
™
(ET-S
TREADLE
ONLY)
6
NYLINER
BEARING
TREADLE
5
PIVOT PIN
TREADLE
ARM
FIGURE 5 - ET-S™ AND ET-S2™ TREADLE EXPLODED LINE DRAWING
All other repairs require replacement of the ET-S™ or
ET-S2™ treadle.
Refer to Figure 5 throughout the procedures.
Remove the pivot pin from the treadle assembly. Gently
release the tension on the treadle spring (7) while removing
the treadle from the treadle arm. Remove the nyliner bearing (6) from the treadle arm.
Treadle Removal:
ET-S™ Treadle
Position the treadle on its side with the potentiometer facing up. Remove the small retaining ring (3) and small nylon
washer (4) that hold the treadle on to the treadle arm and
set aside for the assembly process. After the washer is
removed, pull the treadle off, carefully releasing the pressure from the treadle spring (7). Set the spring (7), nyliner
bearing (6) and the treadle aside for the reassembly process. Inspect rubber treadle cover - replace if necessary .
ET-S2™ Treadle
Position the treadle assembly on its side with the potentiometer facing down. Remove the small retaining ring (3)
and the nylon washer (4) from the treadle pivot pin.
Potentiometer Removal:
Secure the mounting plate. Important: Do not clamp the
assembly by the treadle actuator body or base since
overclamping may cause the casting to be distorted.
Remove the two screws (2) that secure the potentiometer
(1) to the actuator base. The potentiometer (1) can then be
lifted away from the drive shaft.
CLEANING AND INSPECTION
1. Use suitable solvent to clean all metal parts (note that
mineral spirits may damage the paint finish).
2. Inspect the treadle and mounting plate for severe
corrosion, pitting, or cracks. Replace as necessary.
Superficial corrosion and/or pitting is acceptable.
6
NYLINER
BEARING
SPRING
TREADLE
4
NYLON
WASHER
3
RETAINING
RING
7
ET-S2
™
TREADLE
3
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