Product Support Program For Replacing The Service Brake and Parking Brake Light Switches On Certain 416B, 426B, 428B, 436B, And 438B Backhoe Loaders Caterpillar

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.

NOTE: This Program can be administered either before or after a failure. In either case the decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS8054" as the Part Number and "7755" as the Group Number. If administered before failure, use "56" as the Warranty Claim Description Code and use "T" as the SIMS Description Code. If administered after failure, use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.

NOTE: This Revised Service Letter replaces the February 7, 1994 Service Letter. A change was made to the Termination Date.

Termination Date

Problem

The 6T5925 Switch Assemblies of the service brake group and parking brake group may fail or come out of adjustment causing erratic actuation of the stop lights and/or parking brake indicator light on certain 416B, 426B, 428B, 436B, and 438B Backhoe Loaders.

Affected Product
Model & Identification Number

416B (8SG1-4128, 8SG4156-4156 8ZK1-761 )

426B (5YJ1-1043)

428B (7EJ1-1942, 7EJ1946-1949, 7EJ1952-1952)

436B (6MJ1-478)

438B (3KK1-883, 3KK886-886)

Parts Needed

1 9R1968 Spacer

2 9R8189 Push Rod

1 6V2689 Tube-Shrink

3 917473 Splice-Wire

3 1058034 Switch Assembly-Limit

1 1076182 Bracket Assembly

1 1095254 Bracket

3 1100203 Connector Assembly

Action Required

See attached rework procedure.

Service Claim Allowances

NOTE: This is a 4-hour job.

Parts Disposition

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

Attach.

(1-Rework Procedure)

Rework Procedure

Parking Brake

1. Remove the existing 9R9569 Plate and the 6T5925 Switch Assembly attached to it. Refer to Illustration 1.

ILLUSTRATION 1

2. Install a new 9R1968 Spacer and a new 1095254 Bracket as shown in Illustration 1.

3. Cut off the existing two terminals from the wiring harness and splice in a new 1100203 Connector Assembly using two new 917473 Wire Splices. Refer to Illustration 2.

NOTE: Using 40 mm of 6V2689 Shrink Tube, seal off the third (extra) wire of the 1100203 Connector Assembly.

ILLUSTRATION 2

4. Install a new 1058034 Limit Switch Assembly into the 1095254 Bracket. The switch is self-threading.

5. Plug the 1100203 Connector Assembly into the 1058034 Limit Switch Assembly.

6. Actuate the parking brake handle several times. This will automatically adjust the new switch assembly. The parking brake indicator light should come on as the parking brake handle reaches the second to fourth click. If the light does not activate at this setting, check to ensure the parking brake is adjusted correctly.

Service Brakes

Refer to Illustration 3

1. Remove the existing 9R9333 Plate by removing the 8T4138 Bolt and 8T4205 Washer.

2. Remove the 9R2807 Clip and 9R2806 Pin from the back of the 9R8187 Right-Hand Pedal Assembly and the 9R8188 Left-Hand Pedal Assembly to disconnect them from the brake master cylinder. Remove the existing 2-9R8189 Push Rods (change level 1 that are 52 mm long) and replace them with new 9R8189 Push Rods (change level 2 that are 62 mm long).

3. Using a wire, rope, or bungee cord, suspend the brake master cylinder to support it before removing the 9R8183 Bracket Assembly. Remove the bracket assembly by removing the 2-7X2537 Bolts, 4-8T4224 Hard Washers, 2-5C7261 Nuts, 2-8T4136 Bolts, and 2-8T4121 Washers.

4. After the 9R8183 Bracket Assembly is removed, remove the 8T4138 Bolt and 8T4205 Hard Washer to remove the 9R8184 Pin Assembly. This will allow the brake pedals to come loose from the bracket assembly.

ILLUSTRATION 3

Parts Identification Chart for Illustration 3

5. Fabricate two 8-mm thick wedges using structual steel with a yield strength of 290-450 MPa. Refer to Illustration 4.

ILLUSTRATION 4

6. Weld the one wedge of steel onto the top edge of each pedal assembly as shown in Illustration 5.

ILLUSTRATION 5

7. Install the new 1076182 Bracket Assembly to the firewall using the 2-8T4138 Bolts and 2-8T4205 Hard Washers.

8. Install the 2-7X2537 Bolts, 4-8T4224 Hard Washers, and 2-5C7261 Nuts through the bracket and the brake master cylinder. Remove whatever suspension apparatus that was used to support the brake master cylinder in Step 3.

9. Cut off the existing four terminals from the wiring harness and splice in two new 1100203 Connector Assemblies using four new 917473 Wire Splices. Refer to Illustration 6.

NOTE: Using 40 mm of 6V2689 Shrink Tube, seal off the third (extra) wire of each of the 1100203 Connector Assemblies.

ILLUSTRATION 6

10. Install the reworked brake pedals on the new 1076182 Bracket Assembly. Fabricate a 1.5 mm-thick spacer for use in adjusting the pedal travel. Place the spacer between the brake pedal and the pedal stop on the 1076182 Bracket Assembly as shown in Illustration 7. Adjust the clevis on each 9R8189 Push Rod until the pedal touches the pedal stop with the spacer in place.

11. Install the two new 1058034 Limit Switch Assemblies into the 1076182 Bracket Assembly. The switch is self- threading. Screw them into the holes staight and as far as they can go. Illustration 7, below shows an assembled view of the reworked brake pedals, new bracket, and new switches.

ILLUSTRATION 7

12. Plug the two 1100203 Connector Assemblies into the two 1058034 Limit Switch Assemblies.

13. Apply the service brakes a few times so that the pedals contact the new switches. This automatically adjusts the switches. Check for proper brake and brake light accuation.