SPOOL 2S0659 - Caterpillar

2. Connect the LT GR/T wire, that connects to the oil pressure switch, to machine ground. Disconnect the harness plug from the operator panel and check for continuity between connections B and F. (Connection B is the system ground and connection F goes to the oil pressure switch.) Use an 8S4627 Continuity Tester. 3. Check for continuity between the ground connection on the oil pressure switch (B wire) and machine ground. Use an 8S4627 Continuity Tester. 4. Turn the fuel OFF. Remove the oil pressure switch and put a thumb over the opening.Have another serviceman turn the Power Key Switch to the START position so that the starter motor turns the engine. (Do not turn the engine for more than 30 seconds.)An increase in oil pressure must be felt. Brake Pressure Indicator
The brake foot lever controls the air supply to each brake master cylinder. It forces oil to the front and rear disc brakes. There are two different pressure switches in the brake pressure indicator circuit. The two switches are wired in series (wired one after the other in a circuit). If either switch opens, the indicator will flash. If the air pressure for the system is low, the 8N2325 Switch opens and the indicator flashes. When there is too great of a differential in the brake oil pressure to the brake system, the 3V7928 Differential Pressure Switch opens and the indicator flashes. 1. Let engine run for several minutes to be sure there is enough air pressure.2. Check for air leaks, especially at drain valves on air reservoir.3. Check brake fluid level. If the indicator FLASHES only when applying the brake, the problem is probably in the pressure differential between the brakes.Electrical Troubleshooting
1. Remove the LT GR wire from the 8N2325 Brake Pressure Switch and put it to machine ground. If the indicator turns OFF, the problem is in one of the switches or its harness. 2. Check for continuity across the 8N2325 Brake Pressure switch (2-LT GR wires). Use an 8S4627 Continuity Tester. 3. Check for continuity across the 3V7928 Differential Pressure Switch (1-LT GR and 1-B wire). 4. Check for continuity from the differential pressure switch to machine ground. 5. Make sure there is continuity from the 8N2325 Pressure Switch to machine ground. Connect the LT GR wire to the switch again.Disconnect the harness plug from the operator panel and check for continuity between connections B and M (connection B is the ground for the system and connection M goes to the pressure switch). Use an 8S4627 Continuity Tester. Hydraulic Temperature, Engine Coolant Temperature, Or Transmission Oil Temperature Indicator
Follow the instructions given at the first of the section on the monitoring system, to make sure the system is cool enough for the indicator to turn OFF. If the indicator does NOT turn OFF, make a check of the electrical system as follows:1. Disconnect the control wire from the temperature switch of the indicator that is ON. (See TABLE 5). Check for continuity through the switch