Usage:
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 "PS4999" 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 August 1, 1993 Service Letter. Changes have been made to the Affected Product, Parts Needed and Action Required.
Termination Date
August 31, 1994Problem
The three pressure switches mounted to the main control valve may fail due to water entry.The travel and implement/swing pressure switches affect the Automatic Engine Speed Control (AEC) function.If either of these two switches fail, the AEC will not function properly.The boom-up pressure switch energizes the fine control solenoid valve during full boom-up operation.This gives flow Priority to the boom during simultaneous boom-up and stick-in operation.To check this switch, disconnect and measure the resistance in the connector still attached to the switch. The resistance should be infinite in the boom pilot neutral condition. The resistance should be zero when the switch is activated by full boom-up operation.
Affected Product
Model & Identification Number
320 (4ZJ1-479 7GJ1-2342 7WK1-84 8LK1-249 )
320L (8HJ1-526 3XK1-991 9KK1-140 1KL1-141 1TL1-388 2DL1-58 )
320N (9WG1-813)
325 (7TG1-75 8JG1-195 9SG1-255 5WK1-97 8YK1-66 9ZK1-90 )
325L (7CJ1-467 7LJ1-327 2JK1-333 6KK1-186 8NK1-372 2SL1-139 )
325LN (2SK1-450 3LL1-302 )
330 (9NG1-336 9PJ1-75 9WJ1-34 6ZK1-38 )
330L (6SK1-209 6WJ1-358 8FK1-191 2EL1-85 )
330L (8CK1-114)
Parts Needed
Action Required
1. Relieve any pressure in the pilot hydraulic system.
2. Remove the original boom up pressure switch, the travel and implement/swing pressure switches (see Illustration 1).
3. Install the 1028042 Switch Assembly - Boom Up and both of the 1028041 Switch Assemblies. Tighten to 20 ± 4 N·m (15 ± 3 lb ft).
Service Claim Allowances
NOTE: This is a 1.0 hour job.
Parts Disposition
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.
Illustration 1