PRODUCT SUPPORT PROGRAM FOR INSPECTING AND POSSIBLY REWORKING THE RETARDING GRID MOTOR FAN ASSEMBLY ON CERTAIN 795F AC AND 794 AC OFF-HIGHWAY TRUCKS Caterpillar

PRODUCT SUPPORT PROGRAM FOR INSPECTING AND POSSIBLY REWORKING THE RETARDING GRID MOTOR FAN ASSEMBLY ON CERTAIN 795F AC AND 794 AC OFF-HIGHWAY TRUCKS

Usage:

TEBE5702-00

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03Feb2017

A-46

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Before/After	PRODUCT SUPPORT PROGRAM FOR INSPECTING AND POSSIBLY REWORKING THE RETARDING GRID MOTOR FAN ASSEMBLY ON CERTAIN 795F AC AND 794 AC OFF-HIGHWAY TRUCKS
425R 1627 1437 3121		PS45378

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NOTE:

Caterpillar’s obligations under this Service Letter are subject to, and shall not apply in contravention of, the laws, rules, regulations, directives, ordinances, orders, or statutes of the United States, or of any other applicable jurisdiction, without recourse or liability with respect to Caterpillar.

NOTE:

This Program must be administered either before or after failure. In either case the decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS45378" as the Part Number and "7755" as the Group Number. If administered before failure, use "56" as the Warranty Claim Description Code and "T" as the SIMS Description code. If administered after failure, use "96" as the Warranty Claim Description Code, and "Z" as the SIMS Description Code.

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NOTE:

The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.

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TERMINATION DATE

28Feb2019

PROBLEM

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The existing retarding grid motor fan assembly running at altitudes above 3,048m (10,000ft) can fail on certain 795F AC and 794 AC Off-Highway Trucks. If the existing retarding grid motor fan assembly fails it can result in damage to the retarding elements requiring the entire retarder grid to be replaced.

AFFECTED PRODUCT

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Model	Identification Number
794 AC	MT500108-00111
795F AC	ERM00163-00164, 168-169, 205, 264, 270-276

PARTS NEEDED

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Qty	Part Number	Description
24	1K6872	LOCKNUT (After Failure Only)
48	5P1076	WASHER-HARD (After Failure Only)
24	7X0325	BOLT (After Failure Only)
24	8T9389	BOLT (After Failure Only)
In order to allow equitable parts availability to all participating dealers, please limit your initial parts order to not exceed 29% of dealership population. This is an initial order recommendation only, and the ultimate responsibility for ordering the total number of parts needed to satisfy the program lies with the dealer.

ACTION REQUIRED

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The following check is requested every 500 machine hours

1). Access the grid fan blade bolts by removing the screen as shown in the KENR8727 document ?Electric Retarder - Disassemble - Grid Assembly?
NOTE: As shown DO NOT remove the bolts at the ?Z? locations. These are structural and keep the motor assembly attached to the Retarder grid frame. (Image 1)

2). With the screen removed mark/check (Image 2) each of the 24 grid fan blade mounting bolts. There is an underside nut that is not retained so it is not possible to torque the bolt this check is just to verify the bolt is has not loosened. If any bolt looks to have rotated the grid needs to be removed so the bolt can be tightened see the ?Rework Procedures? below.

In the case that Rework is necessary the local Caterpillar dealer is to develop a component exchange strategy to remove/replace the Retarder Grid at PM to reduce machine downtime.

Dealer to perform the retarder grid rework at dealer repair facility.

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Image1

Image2

SERVICE CLAIM ALLOWANCES

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Product smu/age whichever comes first	Caterpillar		Dealer Suggested		Customer Suggested
Product smu/age whichever comes first	Parts %	Labor Hrs%	Parts %	Labor Hrs%	Parts %	Labor Hrs%
0-10000 hrs, 0-36 mo	100.0%	100.0%	0.0%	0.0%	0.0%	0.0%

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NOTE: This is a 1.0-hour job If there has been a previous repair, part age/hours will apply. Retain a copy of the previous repair invoice in the dealer's records for audit purposes, and specify repair date and machine hours in the "Additional Comments" section of the warranty claim.
1 hour labor allowance is to perform Grid Fan Blade Mounting Bolt mark/check procedure as outlined every 500 hours. If any Grid Fan Blade Mounting Bolt fails the check then the Rework Procedure is to be followed and an additional 20 hours is allowed to complete the Rework Procedures.

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PARTS DISPOSITION

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Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.

Rework Procedure

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REWORK PROCEDURE [ON SITE]
1). Refer to KENR8727, Disassembly and Assembly, for removal and installation instructions for the grid, as required, in order to complete the Rework Procedure.
2). Remove the Retard Grid from the machine

REWORK PROCEDURE [OFF SITE]
Refer to Disassembly and Assembly, KENR8727, "Electric Retarder - Disassemble - Grid Assembly", and "Electric Retarder - Assemble - Grid Assembly".

Remove screen (1), with the exception of the bolts in Locations (Z).

NOTE: Removal of the (Z) Mounting Bolts will allow the Grid Fan to become unsupported by the Grid Support Structure.(Image 1.1.1). DO NOT Remove these Mounting bolts.

Image1.1.1

Using a Permanent Pen, mark the element locations. Refer to the Service Manual if/as necessary and Follow the Disassembly Instructions in KENR8727 to remove all four Resistor Elements and the outlet Screen. (Image 1.2.1)

Image1.2.1

With the Grid Assembly laying with the grid fan down (Image 1.3.1)
Remove the bolts and the retaining plate from the top of the fan assembly.(Image 1.3.2)

Install the three guide pins (18, 19, and 20 inches in length into the holes as shown below.(Image 1.3.3)

Image1.3.1

Image1.3.2

Image1.3.3

Use fabric lifting straps that are rated to a minimum of 500 lbs, to lift the fan assembly off of the motor. Make certain that the fan is kept level and square to the rotor as to not make contact with the sides of the rotor coils. (Image 1.4.1)

Place grid fan on cribbing so the cone side is down giving access to the nuts on the back of the grid fan blade bolts

Image1.4.1

Image1.4.2

Remove ONE old grid fan blade mounting bolt.

Note: The grid fan blade assembly is a balanced component so care must be taken to only change ONE bolt at a time of ONE blade at a time with a bolt of the same length. This will assure no blade is put in a different location or slides around. Also all 24 bolts must be changed so the assembly remains balanced.

Compare the old bolt to a 8T-9389 and 7X-0325 bolt. Use the new bolt that is the same length as the old bolt.

Insert the new bolt with washer: Qty 1 Bolt 8T-9389 or 7X-0325 depending on old bolt length & Qty 1 Washer: 5P-1076

Install Qty 1 Washer: 5P-1076 to the bolt on the inside of the grid fan blade assembly

Apply Locktite 263 to the threads of the new Bolt 8T-9389. Apply ~2 drops to the threads just past the washer on the inside of the grid fan blade assembly.

Install Qty 1 Prevailing torque locknut: 1K-6872

Hold the nut and Tighten the bolt to a torque of 111Nm (82 lbft) with a hand torque wrench for the best accuracy.

Apply a torque witness mark using a paint pen across the new bolt head, washer, and fan blade.

Repeat steps above for the remaining fan blade mounting bolts making sure to ONLY replace ONE BOLT AT A TIME with a bolt of the same length.

Image1.5.1

Clean the stator assembly with compressed air. (Image 1.6.1)
Clean the top of the fan mounting surface with a soft cloth. (Image 1.6.2)
Clean the top and bottom of the mounting surface of the fan assembly. (Image1.6.3 and Image1.6.4)

Image1.6.1

Image1.6.2

Image1.6.3

Image1.6.4

Carefully lower the new fan assembly over the guide pins and onto the stator. Make certain that the fan is kept level and square to the rotor as to not make contact with the sides of the rotor coils. (Image 1.7.1)
Remove the guide pins. (Image 1.7.2)
Apply a thin layer of RTV silicone around the bolt holes to prevent any moisture from entering the front of the fan assembly. (Image 1.7.3)

Image1.7.1

Image1.7.2

Image1.7.3

Install the retaining plate. (Image 1.8.1)
Place a thin layer of RTV silicone on the shank of the retaining bolts and re-install. (Image 1.8.2)
Tighten the bolts in a crisscross pattern to 105Nm (Image 1.8.3)

Image1.8.1

Image1.8.2

Image1.8.3

Refer to the Service Manual if/as necessary and Follow the Assembly Instructions in KENR8727 to reinstall all four Resistor Elements, outlet screen, and intake screen.
Install Retarder Grid onto a truck following the installation procedure in KENR8727.