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 "PS8420" 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.
Termination Date
July 31, 1996Problem
The WTL Payload Measurement System may become inaccurate or may fail to work on certain 950F, 960F, 966F, 970F and 980F Loaders.
The components causing the problem may be the pressure sensor and/or the position sensor. The sensors will be replaced only if they are clearly identified as failed after accurate system troubleshooting.
In addition, pressure spikes in the hydraulic system may cause some damages to the pressure sensor affecting its accuracy in pressure readings or causing a major failure. Adding an adapter orifice in the pressure line to the pressure sensor will protect it from pressure spikes. It is strongly recommended to add the adapter orifice on all units as soon as possible.
Affected Product
Model & Identification Number
950F (6YG1-Up 8TK1-3064 )
960F (4CL1-328)
966F (3XJ1-Up 9YJ1-2123 )
970F (9JK1-470)
980F (3HK1-Up 4RN1-502 )
NOTE: This Program applies to any of the above listed units that are equipped with a factory-installed Payload Measurement System or that have been updated in the field with a Payload Measurement System. The factory-installed top level attachment and field-installed kit numbers are 1018322, 1104690 and 1105698.
This Program also applies to any 950B, 950E, 966D, 966E and 980C that have been updated in the field with a Payload Measurement System. The field-installed kit numbers are 2Z9132, 2Z9136 and 2Z9137.
Parts Needed
For Adapter Orifice Installation
For Pressure Sensor Replacement
For Position Sensor Replacement
- 1 - 1237416 Control Group
Action Required
Parts Stock
Remove all 1032040 Pressure Sensor Groups and all 1108190 Control Groups from Parts Stock.
Affected Product
See attached rework procedure.
Service Claim Allowances
Parts Stock
Submit one claim for all 1032040 Pressure Sensor Groups and 1108190 Control Groups removed from Parts Stock.
Affected Product
Parts Disposition
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.
Attach.
- (1 - Rework Procedure)
Rework Procedure
NOTE: There are three separate sections to this rework procedure. Section 1 concerns the installation of the adapter orifice, Section 2 concerns the replacement of the pressure sensor and Section 3 concerns the replacement of the position sensor.
Section 1 - Installation Of An Adapter Orifice
1. Release all hydraulic pressure in the hydraulic tank and lines.
2. Install a new 1222222 Adapter, 1J9671 Seal-O-Ring and 6V8397 Seal-O-Ring in the line to the pressure sensor at the end of the hose away from the sensor as shown in the Illustration below.
3. After installing the adapter, calibrate the Payload Measurement System.
NOTE: If a machine has already been equipped with an experimental orifice, this Program still applies and the machine should be reworked again.
Section 2 - Replacement Of The Pressure Sensor
NOTE: Before this Program can be applied, it must first be verified that the pressure sensor is at fault. Pressure sensor failure may be indicated by:
- A. Position sensor failure.
- B. Improper calibration procedure (not running at high idle, or using too small a calibration weight, for example).
- C. .Position sensor not adjusted to provide sufficient travel.
- D. Hydraulic system problems causing slow raise speed, etc..
- B. Improper calibration procedure (not running at high idle, or using too small a calibration weight, for example).
Once pressure sensor failure is verified, repair as follows:
1. Release and then verify that all hydraulic pressures, tank and line residual, have been removed from the system.
2. Remove the existing pressure sensor and install a new 1244672 Control Group.
3. Confirm that a 1222222 Orifice has been installed at the end of the pressure sensor hose away from the sensor.If the 1222222 Orifice has not been installed, install one as detailed in Section 1.
4. Calibrate the payload measurement system.
5. Check for normal operation.
Section 3 - Replacement OF The Position Sensor
NOTE: Before this Program can be applied, it must first be verified that the position sensor is at fault. Position sensor failure may be indicated by:
- A. Pressure sensor failure.
- B. Improper calibration procedure (not running at high idle, or using too small a calibration weight, for example).
- C. Position sensor not adjusted to provide sufficient travel.
- D. Damaged position sensor linkage.
- E. Hydraulic system problems causing low lift speed, etc..
- B. Improper calibration procedure (not running at high idle, or using too small a calibration weight, for example).
Once position sensor failure is verified, repair as follows:
1. Remove the existing position sensor and install a new 1237416 Control Group. Be careful not to force the new sensor to travel past its rotation stops.
2. Adjust the sensor according to the Service Manual procedure.
3. Check for proper position sensor travel (refer to the Service Manual Supplement, SENR6756, page 6).
4. Calibrate the payload measurement system.
5. Check for normal operation.