Missing Speed Signal The payload meter uses the speed signal to measure distances and speeds. It is the speed signal that causes the payload meter to sample pressure data to estimate payload just after loading. After the truck travels 160 m (0.10 mi.) the payload meter records the payload estimated using the data captured just after loading. During the 160 m, the payload meter displays a count. When the payload meter is set to display metric units, it counts up to 160 m. When English units is selected, it counts up to 0.10 mi. This 160 m (0.10 mi) is designed to allow the truck to repo- sition around the shovel during loading.
If the speed signal is missing, the payload meter captures suspension data when the body rises at the dump. Without the speed signal, the payload meter cannot determine that the truck has begun moving after loading. In addition, it cannot measure the 160 m from the loading site. While the truck is loaded, the payload meter will dis- play live payload estimates. When the truck is empty, the payload meter will display 0. The haul cycle data stored in memory will have 0 recorded to max speed and haul cycle distance. F-18: Alternator R-Terminal, Oil Pressure Signals The PLM II™ monitors engine hours using the alternator R-terminal and oil pressure signals.
The payload meter will register a fault if both signals are not present. For the R-terminal input to the payload meter, 24v=engine running and 0v=engine stopped. For the oil pressure input to the payload meter, open=engine running and ground=engine stopped. It is recommended that these inputs be modified to indicate that the engine is running at all times. Connect the R- terminal input to payload meter to the keyswitch (712) signal. Disconnect and tape back the oil pressure signal to the payload meter. These changes will cause the payload meter to always consider the engine to be ON. There are 2 effects from this change.
On power-up, the payload meter will not show the normal sequence of displays. This is not usually a prob- lem. The payload meter cannot be re-initialized. This extremely rare procedure is used to reboot the payload meter. Shorted 18v Sensor Power Supply (930E) The 18v sensor power supply, circuit 39F, comes from the payload meter and branches out to the inclinometer and pressure sensors. The connection for this is made approximately 30.5 cm (12 in.) from the connection at the back of the cab, just above the wheel.
This can be a common point of failure and should be the first place to check when the pressure sensor values drift erratically while the truck is sitting still or the payload meter indicates shorts on all the pressure sensors. The harness may be repaired with a butt splice, or a new harness can be purchased and installed. M20007.2 3/02 Payload Meter II™ Troubleshooting M20-37