Field Installation Procedure for Redundant Electronic Overspeed Protection{1915} Caterpillar

Engine:

3508B (S/N: CNB1-UP; PTN1-UP; BGX1-UP)

3512B (S/N: CMC1-UP; BLF1-UP; PTF1-UP; BRK1-UP; PTM1-UP)

3516B (S/N: CPA1-UP; BMB1-UP; BPJ1-UP; FDN1-UP; PPS1-UP)

Introduction

This Special Instruction provides the information that is necessary to install the 234-8721 Box Group

All 3500B Engines are controlled by an Electronic Control Module (ECM). The ECM monitors engine RPM. The ECM will also disable fuel injection when an overspeed condition occurs. The 234-8721 Box Group provides redundant overspeed protection through an independent speed sensing system. When the 234-8721 Box Group is activated, the Box Group interrupts power to the ECM. The engine will shut down.

Note: Reference 236-2104 Mounting Group for cylinder head rocker box mounting details.

The 236-2104 Mounting Group includes the parts that are listed in Table1.

Operation

234-8721 Box Group is equipped with a two-position switch labeled OFF/RESET and ON. With the switch in the ON position, the green lamp labeled "SPEED SWITCH POWER" will be lit. In the event of an engine overspeed shutdown triggered by the 234-8721 Box Group , the red lamp labeled "ENGINE OVERSPEED" will be lit. After troubleshooting and correcting the cause for the overspeed, the selector switch needs to be momentarily placed in the OFF/RESET position. Placing the two-position switch in the OFF/RESETposition,will reset the speed switch.

Return the selector switch to the ON position for normal operation.

To disable the Box Group in the event of a component failure, perform the following two steps.

1. Place the two-position switch in the ON position.

2. Place the circuit breaker that is contained in the 234-8721 Box Group in the OFF position.

By performing the two steps above, the 234-8721 Box Group is deactivated. This allows the engine to operate without the redundant overspeed protection system. The engine will continue to be protected by the ECM.

Installation Instructions

Note: For EPG engines manufactured after 1January 2004, skip steps 2 through 5 and remove the ECM power connector jumper plug and install the 6 pin Deutsch connector in the ECM power connector. For engines manufactured before 1January 2004, use steps 2 through step 5.

1. Mount the 234-8721 Box Group on the side of the engine on the cylinder head rocker box. If the box group is not mounted on the engine, it must be located where the magnetic pickup harness will reach the flywheel housing. Also make sure the six wire ECM harness will reach the engine ECM

2. Remove the 24 volt power source to the engine.

3. Remove the C-Key plug assembly (1) from the engine ECM. Refer to Illustration 1.

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Illustration 1	g01049591

4. From the C-Key plug, locate and remove the wires at pin locations 4 and 6 (Battery+, 150-RD14). Also remove the wire from pin location 5 (Battery-, 229-bk-14).

5. Using the six wire harness supplied with the 234-8721 Box Group , insert the three wires that were removed from the ECM C-Key plug into the six pin Deutsch connector. Reference table 2.
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   Table 2

   WIRES FROM ECM Plug Location	TO Deutsch Connector Location
   4	1
   5	2
   6	3

6. Place the three wires from the 6 pin connector into the ECM C-Key plug utilizing Table 3.
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   Table 3

   WIRES FROM Deutch Connector Location	TO ECM Plug Location
   4	4
   5	5
   6	6

   Note: Wires need to be routed inside the rubber boot (2). Reference illustration 2.

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Illustration 2	g01049823

7. Remove one of the plugs from the top of the flywheel housing, insert the magnetic pickup that is supplied with the 237-5334 harness assembly (3) as shown in illustration 3 until it contacts the flywheel ring gear, turn the magnetic pickup 1/2 turn counter clockwise in order to clear the flywheel and lock down jam nut.

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Illustration 3	g01049841

8. Using 7K-1181 Plastic Ties , secure both harnesses to the engine harness, coil any excess harness and secure.

   Note: Both harnesses can easily be shortened to a custom length by cutting the harness at the end opposite the 234-8721 Box Group .

9. Stop the engine and locate the speed switch adjusting wheel lock screw (4). Reference illustration 4.

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Illustration 4	g01049854

10. Follow the steps below in order to adjust the speed switch.

    1. Loosen the adjusting wheel lock screw.

    2. Turn speed switch switch adjusting wheel to 100.

    3. Start the engine and operate at rated speed.

    4. Depress and HOLD the "85% overspeed verify" button and slowly turn the speed switch adjusting wheel toward the lower numbers until the engine shuts down.

       Note: The Red "Engine Overspeed Lamp" that is located on the front of the 234-8721 Box Group should illuminate at this time.

    5. Turn the switch on the 234-8721 Box Group to the OFF/RESET position and then turn the switch back to the ON position.

       Note: The red "Engine Overspeed Lamp" should go off at this time.

    6. Restart the engine and operate at rated speed.

    7. Depress the "85% overspeed verify activation" button and verify that the engine shuts down. If the engine shuts down proceed to step 10.h. If the engine continues to run, slowly turn the speed switch adjusting wheel toward the lower numbers until the engine shuts down. Repeat steps 2, 3, and 4 in order to verify that speed adjustment is correct.

    8. Tighten the adjusting wheel lock screw. The adjustment is complete.

System Schematic

Illustration 5	g01051683