3126B MARINE ENGINE Caterpillar

Battery Circuit Requirements

Usage:

Negative Battery Bus Bar Connections

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All negative battery connections for electronic and electrical components in the electronic control system for marine engines must have a common ground that terminates at the Negative Battery Bus Bar. Improper grounding can cause unreliable and uncontrolled circuit paths. The engine may unexpectedly go to low idle, may fail to shut down, or may fail to change engine speed in response to the control system. Failure of the engine to respond to the control system could result in injury or death. When the electronic control system is installed, modified or repaired, all electronic circuits should be tested for correct installation and operation with the Electronic Control Module (ECM) and the electronic control system before the engine is started.

The alternator, the starting motor and all electrical systems must be grounded to the negative terminal of the battery. The alternator and the starting motor must also meet electrical isolation requirements for marine applications. If the engine has an alternator that is grounded to an engine component, a ground strap must connect the grounded component to the negative terminal of the battery. Also, the component must be electrically isolated from the engine.

Negative Battery Terminal Connection

A bus bar is recommended for use as a dedicated common connection to the negative battery terminal for all components that require a negative battery connection. Refer to "Power Supply Connections To The Starting System" in this manual for additional information. This bus bar should be directly connected to the negative battery terminal.

Use of the bus bar ensures that the ECM and all connected components have a common reference point. Connected components include switches, sensors, and electronic display modules.

Starting System Schematic

Figure 22 - Starting System Schematic for 3126B Marine Engine

Abbreviations for Figure 21 - "Starting System Schematic for 3126B Marine Engine":

* A "Amp"

* ALT "Alternator"

* BAT. "Battery"

* -BAT. "Negative battery circuit"

* -BATTERY BUS BAR "Negative Battery Bus Bar"

* +BAT "Positive battery circuit"

* +BATTERY BUS BAR "Positive Battery Bus Bar"

* +BATTERY (SWITCHED) "Switched Positive Battery circuit"

* +BATTERY (UNSWITCHED) "Unswitched Positive Battery circuit"

* BK "Black"

* BR "Brown"

* BU "Blue"

* CB "Circuit breaker"

* CISS "Customer installed start-stop switch"

* CPSS "Customer provided shutdown switch"

* GY "Gray"

* MTR "Connection for starting motor"

* PK "Pink"

* PU "Purple"

* PWR "Power"

* RD "Red"

* REMOTE SHUTDOWN INPUT "Shutdown input circuit"

* REMOTE START "Remote start circuit"

* SM "Starting motor"

* SMMS "Starting motor mag switch"

* SW "Switch"

Power Supply Connections to the Starting System

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All negative battery connections for electronic and electrical components in the electronic control system for marine engines must have a common ground that terminates at the Negative Battery Bus Bar. Improper grounding can cause unreliable and uncontrolled circuit paths. The engine may unexpectedly go to low idle, may fail to shut down, or may fail to change speed in response to the control system. Failure of the engine to respond to the control system could result in injury or death. When the electronic control system is installed, modified or repaired, all electronic circuits should be tested for correct installation and operation with the Electronic Control Module (ECM) and the electronic control system before the engine is started.

Table 7: Allowable Wire Length to Connect Starting Motor to the Battery

"Allowable Wire Length to Connect Starting Motor to the Battery" gives the size of wire and the maximum allowable length of the wire that is recommended to connect the battery to the starting motor.

The size of wire to the positive battery which supplies the power to electrical and electronic components must be of adequate size to carry the maximum current of the circuit.

The size of wire to the Negative Battery Bus Bar to which electrical and electronic components have a common connection must be of adequate size to carry the maximum current of the circuit.

The causes of intermittent shorts or power interruptions are often very difficult to identify. Proper wire connections for all electrical systems and connection to a common negative bus bar on the vessel are necessary for the correct performance and reliability of the engine.

The alternator, the starting motor, and all electrical systems must have a common with the negative battery terminal. The alternator and the starting motor must conform to electrical isolation requirements for marine applications. If the alternator is grounded to an engine component, a ground strap must connect that component to the negative battery terminal. Also, that component must be electrically isolated from the engine.

Figure 23 - Minus Battery Connections of Operator Stations for a Two Engine Arrangement

All negative battery connections on the components should be directly wired to the Negative Battery Bus Bar. Wire that is a minimum size of 12 AWG should be used to connect the operator stations to the Negative Battery Bus Bar that is located in the engine room.

Negative battery connections that conform to Figure 22 "Minus Battery Connections of Operator Stations for a Two Engine Arrangement" ensure that all components in the electrical system have the Negative Battery Bus Bar in the engine room as a common reference point. Reliable operation of the electrical system requires that all of the components in the system are correctly connected.

All wires for +Battery and -Battery Bus Bar to the P61 Customer Connector should have a wire size of 14 AWG.

Positive Battery Circuit for ECM Power

Do not use fuses for circuit protection. Circuit breakers should be used for circuit protection. Circuit breakers should be located with other circuit protection for the vessel in a dedicated panel that is centrally located.

If automatic reset circuit breakers are used, the location of the circuit breaker is critical. The trip point of these circuit breakers can be significantly reduced below the rated trip point if exposed to high temperatures which could cause intermittent shutdowns. Troubleshooting can easily fail to detect this problem which can result in incorrect replacement of components.

Use of dedicated circuit protection will reduce the possibility of system performance that is degraded due to voltage transients. Additional electrical loads should not be connected between the ECM and the circuit protection.

The ECM Switched Positive Battery terminal keyswitch is connected to Customer Connector P61 pin 30.

When the ECM is energized, the current for this circuit is 6 milliamperes with 24 VDC. The wire does not require a dedicated protected circuit. However, a dedicated protected circuit is recommended. The circuit protection should be rated at 5 amperes with a minimum of one ampere.

To prevent engine shutdown in the event of a short circuit in the vessel wiring harness, the electronic control system must be powered on a dedicated protected circuit. The wire size should be 14 AWG. This connection should be made through the Switched Positive Battery circuit so that the electronic control system will be powered when the start switch in the ON/RUN position.

Switched Positive Battery Circuit

Figure 24 - Unswitched Positive Battery Connections

The installation requires three Unswitched Positive Battery circuit in addition to the Switched Positive Battery circuit that is described in "Switched Positive Battery Circuit for Power to the ECM" section of this manual. The Unswitched +Battery connection is made to the Customer Connector P61 pins 1, 5, and 8. The connection of the other end of the wire can be made to any Unswitched Positive Battery connection on the vessel.

The size of circuit breaker depends upon the number and the type of displays that are installed.

The ECM and the monitoring display must be powered from the same switch which provides a single power source. The same battery source must be used for all positive battery and negative battery connections.

Welding Guidelines for Engines with Electronic Controls

Proper welding procedures are necessary to avoid damage to the electronic control module and associated sensors and components. The following procedures should be followed when welding on any engine or application that uses electronic controls:

* Stop the engine. Put the start switch in the OFF position.

* Disconnect the negative battery cable at the battery. If a battery disconnect switch is provided, put the switch in the OPEN position. Do not use electronic components such as the ECM, sensors, and ground straps as ground points for the welder. Do not use fuel system components or lubrication components for grounding the welder.

* Connect the clamp for the ground cable of the welder directly to the part or component area to be welded. Place this clamp as close as possible to the weld to reduce the possibility of damage by the welding current. Components which can be easily damaged include bearings, hydraulic components, and electronic/electrical components.

* Protect any wiring harness from welding debris and spatter.

* Use standard welding procedures to weld the materials.

Suppression Of Voltage Transients

The installation of transient suppression at the source of the transient and at the ECM is recommended. An environmental standard for electrical components and systems that is equal to or more stringent than SAE J1455 should be followed.

The use of inductive devices such as relays and solenoids can result in the generation of voltage transients in electrical circuits. Voltage transients that are not suppressed can exceed the specifications of SAE J1455 which will degrade the performance of the electronic control system.

The OEM should specify relays and solenoids that have voltage transient suppression that is part of the component.

Figure 25 - Voltage Transient Suppression in a Relay Using a Diode

(A) Suppression of transient voltage in a relay with a low side driver or switch

(B) Suppression of transient voltage in a relay with a high side driver or switch

Refer to Figure 24 - "Voltage Transient Suppression in a Relay Using a Diode" for examples of transient voltage suppression in a relay that uses a diode. Another method of transient voltage suppression is the use of a resistor with the correct resistance in parallel with a solenoid coil or relay coil.

Inductive devices such as relays or solenoids should be located to maximize the distance from components of the electronic control system. Wiring harnesses that are installed by the OEM should be located to maximize the distance from the wiring harness of the electronic control system to avoid the inductive coupling of noise transients.

Installation

Parts Required

The following chart is for ordering the total parts required for one basic engine installation. Refer to the individual installation topics for the specific parts (and quantity) required. Items and quantity will vary according to the installation options chosen.

Customer (OEM) wiring and optional features are recommended. Elimination of any components shown in this installation guide will disable certain engine features. Contact Caterpillar, Inc. when considering component removal. No additional connections are allowed as detailed and described in this publication without Caterpillar, Inc. approval.

Table 8: Basic Parts Required for Installation of single engine.

Avoid splicing or soldering wire connections. All wire connections mentioned and illustrated in this guide should be terminated at terminal strips. This practice will ensure engine and system reliability.

Throttle Position Sensor

The Throttle Position Sensor (TPS) eliminates the mechanical throttle and governor linkages. The TPS utilizes the lever movement by the operator to send an electrical signal to the ECM for the engine. The TPS signal and the speed/timing signal are processed by the ECM to control engine speed.

The output of the sensor is a constant frequency signal with a pulse width that varies with the throttle position. The pulse width measures the duty cycle. The Pulse Width Modulated (PWM) signal is expressed as a percentage of the duty cycle.

Figure 26 - Duty Cycle

Figure 27 - PWM Definition

Figure 28 - Throttle Position Percent versus PWM Input

PWM Input Requirements

The following criteria are required for the correct operations of a Non-Caterpillar throttle position sensor:

* Active pull up/ pull down with output protection

* Sensor stop-

Low Stop 7.5 ± 2.5%

High Stop 92.5 ± 2.5%.

* Output frequency-

Minimum of 300 Hz

Nominal of 500 Hz

Maximum of 700 Hz

* High output voltage-

Minimum of 4.5 VDC

Maximum of 32.0 VDC.

* Low output voltage

Minimum of -0.3 VDC

Maximum of 0.5 VDC

* Sink current

1.5 mA

* Source current

2.0 mA

* Output linearity ±2.5% duty cycle vs. throttle lever position.

Figure 29 - ECM Test Circuits

Engine Synchronization Switch

The purpose of the engine synchronization switch is to link multiple engine ECM's to a single throttle on the vessel. The single throttle controls the engine speed for all the engines. This feature improves the control of the vessel and adds operator convenience.

A single throttle control for vessels that have multiple engines is standard practice which allows the transfer of throttle control to any other throttle.

Table 9: "Code for Synchronization of Throttle Controls" gives the code that determines the synchronization of throttle controls. The synchronization function can only be activated or deactivated when the desired engine speed of all engines are within 50 rpm of each other.

Table 9: Code for Synchronization of Throttle Controls

Multiple Synchronization Switch Installations

The 3126B Marine Engine supports single station throttle synchronization. The synchronization is accomplished by the use of two switch inputs on each ECM to determine the throttle synchronization. The engine ECM is not designed to support synchronization switches from multiple stations.

Multiple stations complicate the wiring and typically require some method of transferring control from one station to another station. The transfer of control may be accomplished by several methods. The boat builder or installer is responsible for determining the method and ensuring proper operation of synchronization.

If multi-station synchronization switches are installed, care MUST be taken to prevent both of the synchronization inputs (Connector J61 pin 34 and pin 35) from being connected to the Negative Battery Bus Bar. If both synchronization inputs are low, the ECM will only monitor its primary throttle and the synchronization inputs will be ignored. Care MUST also be taken to ensure that a positive battery to negative battery SHORT CIRCUIT does not occur in the wiring for the synchronization switches.

Throttle Control for Single Engine Installation

Figure 30 - Throttle Position Sensor Connections for a Single Engine Installation

Table 10: Throttle Switch Positions

Table 11: Parts for Single Engine Installation

Synchronization for Two Engines

Figure 31 - Throttle Position Sensor Connections for a Two Engine Synchronization

Table 12: Code for Synchronization of Throttle Controls

Table 13: Parts for Two Engine Installation

Calibration of Throttle Position Sensor

Calibration of the Throttle Position Sensor requires the CAT Electronic Technician (ET) Electronic Service Tool.

Refer to "3126B Marine Engine Troubleshooting", RENR2243 and the "Tool Operating Manual", SEHS9199 for procedures to calibrate the Throttle Position Sensor.

Throttle Linkage

Inspect the throttle linkage for components that are:

* loose

* bent

* broken

* missing

* worn

The throttle linkage should operate without binding or excessive drag. The sensor when not connected to the throttle should return to low idle within one second.

1. Turn the keyswitch to the OFF position.

2. Connect the ET Electronic Service Tool to the Service Tool Connector.

3. Turn the keyswitch to the ON position. Do not start the engine.

4. Observe the indication for duty cycle on the Monitor Throttle Position Sensor Signal screen of the Electronic Service Tool.

5. Place the throttle lever in the position for low idle. Adjust the throttle linkage. Adjust the low idle set screw.

When in low idle, the duty cycle should be between 5 and 10 percent. When the throttle lever is moved from the position of low idle after the adjustment is completed, the duty cycle should increase.

6. Place the throttle lever in the position of high idle. Adjust the throttle linkage. Adjust the high idle set screw.

When in high idle, the duty cycle should be between 90 and 95 percent. When the adjustment of high idle is made on some types of linkage, that adjustment may change the low idle position. Repeat the adjustment for low idle to verify that the low idle is correctly adjusted.

Figure 32 - Calibration Screws for Throttle Pedal Position

Synchronization for Three Engines

Figure 33 - Throttle Position Sensors Connections for Three Engine Synchronization

Synchronization for Four Engines

Figure 34 - Schematic for Connecting Throttle Position Sensors for Four Engine Synchronization

Remote Shutdown Switch

When the Remote Shutdown Switch closes, the ECM disables the fuel injection signal. This action causes the engine to shut down. The ECM remains powered and active.

Table 14: Parts Required for Installation of Remote Shutdown Switch

Figure 35 - Connection for Remote Shutdown Switch

Trolling Mode Input

When the Trolling Mode is in operation, the full range travel of the throttle lever causes the engine speed to change from low idle to the maximum programmed trolling speed. The Trolling Mode only engages if the engine speed is within 30 rpm of low idle. Trolling Mode can also be activated when the engine is shut down.

When the transmission is in Trolling Mode, the switch input for the Trolling Mode is connected to the Negative Battery Bus Bar. The activation of the trolling valve must automatically connect the switch input of the Trolling Mode to the Negative Battery Bus Bar.

Table 15: Parts Required for Installation of Trolling Mode Actuation

Figure 36 - Connection for the Trolling Mode Actuation

Slow Vessel Mode Switch

When the slow vessel mode switch closes, the ECM reduces the programmed low idle to 550 rpm. This feature improves the maneuverability of the vessel in docking and no wake zones.

Table 16: Parts Required for Installation of the Slow Vessel Mode Switch

Figure 37 - Connection for the Slow Vessel Mode Switch

Trip Clear Switch

When the Trip Clear Switch is activated, the ECM clears the trip data. Then, the ECM starts a new trip log. This action clears the trip histograms and the trip total. The lifetime totals are not cleared.

Table 17: Parts Required for Installation of the Trip Clear Switch

Figure 38 - Connection for Trip Clear Switch

Air Inlet Heater Installation

The Air Inlet Heater (AIH) is used to improve cold start capability of the engine and to reduce white smoke. The ECM controls the AIH Grid through the Air Inlet Heater Relay. The AIH operation is determined at three different times, Power Up/Preheat, Cranking, and Engine Started Cycle. The OEM is responsible for connecting the contact side of the AIH relay to battery voltage. Recommended circuit protection for this connection is 130 Amps with a circuit load of 100 amps continuous. The ECM AIH driver is a low side driver sinking 1.5 A maximum.

Figure 39 - Air Inlet Heater Schematic

ECM Driven Warning Alarm and Diagnostic Lamps

The ECM provides drivers capable of sinking or sourcing 300mA, which can be used to drive a relay or audible/visual alarms to indicate various diagnostic conditions.

Driver Specifications

Electrical specifications for the ECM low side and high side drivers used for the Diagnostic Lamp and Warning/Alarm Lamps allow a maximum load current of 0.30 amperes (300mA). The ECM does not provide diagnostic codes associated with either lamp circuit.

Figure 40 - Low Side Driver (Sinking Driver)

Low side ECM drivers provide a path to the -Battery Bus Bar to activate a lamp or other device connected to it. Caterpillar, Inc. does not require dedicated circuit protection for these circuits.

Figure 41 - High Side Driver (Sourcing Driver)

High side ECM drivers provide a path to +Battery to activate a lamp or other device connected to it. Caterpillar, Inc. does not require dedicated circuit protection for these circuits.

Diagnostic Lamp Operation

The Diagnostic Lamp alerts the operator to the presence of active diagnostic codes. A diagnostic code indicates a fault condition in the electronic control system. The operator uses this indication to diagnose component failures in the electronic control system.

Viewing Diagnostic Flash Codes

Caterpillar has developed a proprietary two digit diagnostic flash code. The two digits can be determined by observing the Diagnostic Lamp. The lamp will flash to identify the flash code. The flash code identifies active codes that have occurred after the ECM is energized.

A diagnostic lamp installed by an OEM is required to indicate a diagnostic condition flash code to the operator.

Determine the flash code by the following procedure:

1. Count the flashes on the Diagnostic Lamp to determine the first digit.

2. A two second pause will occur before the lamp flashes for the second digit.

3. Count the flashes to determine the second digit.

4. If more than one diagnostic condition has occurred, all of the active codes that have been received since the ECM was energized will be displayed. The two digit code for each diagnostic condition will flash with a five second pause between the flash codes.

The diagnostic flash codes should only be used to indicate the nature of the occurrence of a diagnostic condition. The flash codes should not be used to perform detailed troubleshooting. Troubleshooting should be performed using diagnostic codes that are displayed by an Electronic Service Tool.

Optional Diagnostic Lamps

The Caterpillar electronic monitoring system offers optional warning lamps that can be installed by the OEM. These warning lamps alert the operator to the occurrence of several fault conditions that are detected by the ECM. The prompt observance of these fault conditions by the operator provides greater protection of the engine.

The following procedure determines if the Warning Lamp circuit is functional:

1. Turn the ignition switch to the ON position. Do not start the engine. When the switch is in the ON position, the ECM is energized.

2. The ECM will turn the Warning Lamp on for five seconds.

3. If the lamp circuit functions correctly, the Warning Lamp will turn off unless a fault condition exists.

An OEM installed Warning Lamp is required to indicate a potentially engine damaging problem determined by the electronic monitoring system.

Warning Indicator Lamp or Alarm

The lamp or alarm alert the operator that a fault condition has occurred. If the following events occur, the Warning Lamp or the audible alarm, if equipped, are activated:

* A warning event code is active - Warning Lamp on solid

* The engine is in the derate mode - Warning Lamp Will Flash

When the ECM is energized, the warning indicator lamp will turn on for five seconds. Then, the lamp will turn off unless the ECM detects that an engine event is active.

Low Oil Pressure Lamp

The low oil pressure lamp indicates the occurrence of low oil pressure. This diagnostic is determined by the ECM based upon the relationship between the engine speed and the actual oil pressure.

When the ECM is energized, the low oil pressure lamp will turn on for five seconds. Then, the lamp will turn off unless the ECM detects a low oil pressure condition.

High Coolant Temperature Lamp

The high coolant temperature lamp indicates the occurrence of high coolant temperature.

When the ECM is energized, the high coolant temperature lamp will turn on for five seconds. Then, the lamp will turn off unless the ECM detects a high coolant temperature condition.

Warning Lamp Installation

Figure 42 - Schematic of Warning Lamps and Alarms

Table 18: Parts for Warning Lamp Installation

Warning Alarms Requiring More Than 300 Milliamperes

Figure 43 - Schematic for Warning Lamps and Alarms Requiring More Than 300 Milliamperes.

Remote Tachometer

Figure 44 - Remote Tachometer Connection

1. Connect from the J61 Customer Connector pin-14 (Tachometer +) to the Tachometer signal input 1.

2. Connect from the J61 Customer Connector pin-15 (Tachometer -) to the Tachometer signal input 2.

3. Connect +Battery to the +Battery input on the Tachometer.

4. Connect from the -Battery Bus Bar to the Tachometer -Batt (GND) terminal.

5. Connect an Electronic Service Tool to the Service Tool Connector and proceed to the Customer Parameters Screen.

6. Calibrate the ECM signal to the pulses per revolution (ppr) for your Tachometer signal.

NOTE: Either one of the two signal lines from the ECM can be used for tachometers will a single input terminal. The remaining signal line should be left disconnected.

The tachometer engine speed calibration is 113 ppr.

Hour Meter (Optional)

The ECM provides a signal for the hour meter. When the ECM reads an engine speed that is greater than 500 rpm, the ECM turns on the hour meter. This signal is actual engine hours.

Table 19: Parts Required for Installation of Trolling Mode Actuation

Figure 45 - Connections for Hour Meter

Maintenance Lamp/Indicator Mode

Maintenance Indicator Mode

Factory Default: OFF

Programming Range: OFF, Manual Hours, Manual Fuel, and Auto Hours

Function: Allows customer to turn maintenance indicator off or on. Determines whether maintenance interval will be displayed as fuel or hours. In manual mode, the user may define user interval for PM1.

Maintenance Indicator PM1 Interval

* OFF - Default

* Manual Hours - The number of engine hours to service.

* Manual Fuel - The number of gallons of fuel to service.

* Auto Hours - The ECM automatically calculates time to service based on recorded fuel consumption and oil sump capacity.

If PM1 is programmed to automatic, the ECM calculates the next maintenance due by considering the engine operation history from the previous maintenance interval. If the engine has a history of poor fuel economy, the maintenance indicator will occur sooner than it would on an engine with better fuel economy.

Maintenance Indicator Lamp

When the preventive maintenance interval occurs, such as PM Level 1, the maintenance indicator lamp turns on.

When running against the fuel to air ratio control map, the lamp turns on for 90 seconds.

When the ECM is energized, the maintenance indicator lamp will turn on for five seconds. Then, the lamp will turn off unless the ECM detects that a maintenance interval has occurred.

Maintenance Clear Switch (Optional)

The maintenance clear switch is required to reset the PM1 diagnostic for the maintenance indicator after maintenance on the engine is performed.

Table 20: Parts Required for Installation of the Maintenance Clear Switch

Figure 46 - Connection for Maintenance Clear Switch

Communication Data Links

The ECM provides output pins that are dedicated to the communication data link. The data link is available to share data between the ECM, electronic service tools, and electronic display modules.

The engine is equipped with an Engine Service Tool Connector. An additional Customer Supplied Service Tool Connector may be installed for improved accessibility.

Optional Remote Electronic Service Tool Connector

The optional Electronic Service Tool Connector is installed by the customer or Original Equipment Manufacturer (OEM).

Table 21: Parts for Optional Electronic Service Tool Connector

The Electronic Service Tool will operate when the engine is running. The Electronic Service Tool will also operate when the engine is not running, but with the ignition switch in the ON position.

Figure 47 - Schematic of Data Link Connections for the Remote Service Tool

The Negative Battery Bus Bar circuit on the Remote Electronic Service Tool Connector pin B must be connected directly to the Negative Battery Bus Bar. This circuit must not be connected to the negative battery terminal through any other path.

All wires for the data link should be twisted pairs of 18 AWG wire. The wire pair should have a minimum of one twist per 25 mm (1.0 inch). The length of the wire between the remote electronic service tool and the Customer Connector J61 should not exceed 30 m (98.4 ft).

CAT Data Link

The CAT Data Link is a proprietary communication medium available on Caterpillar Marine Engines. The CAT Data Link is for communication with other Caterpillar microprocessor based devices such as the Electronic Control Module, Engine Monitoring System (EMS), Global Positioning System (GPS), and the Engine Vision Interface Module (EVIM).

Data Loops

A device that is incorrectly wired or incorrectly connected to the CAT Data Link will result in a data loop that will cause the CAT Data Link to function improperly.

The following precautions will help prevent data loops and improve reliability of the data link system:

* Use 143-5018 Data Wire (18 AWG) for connecting components to the data link.

* Use a dedicated terminal strip for data link connections.

* Terminate all wires at terminal strips.

* Locate the terminal strip so that the length of the wire between data link connections is minimized.

* The total length of data link wires should not exceed 30 m (100 ft).

* Only one set of twisted pair data wires should be installed to the bridge displays.

* The data link wires should be installed from the terminal strip in the engine room to the first station. Only one set of twisted pair data link wires should be run to the bridge displays.

* If a second station utilizes a Caterpillar display group, the data link wires should be installed from the engine room terminal strip to the first station and continued from the first station to the second station.

* Do not splice wires.

* Do not solder wires.