SWITCH AS 1114788 - Caterpillar

Complete Overhaul Instructions
General
This manual is not intended to provide information regarding the repair of the electronic circuit board. Such faults are difficult to trace without specialized equipment and training. Where electronic faults are suspected the tester should be returned to the Sales Office. Physical damage to display and keyboard may occur and can be checked as follows.To remove Top Panel
Remove 6 screws from top panel and angle up the bottom of the panel 51 to 76 mm (2.0 to 3.0 inch). Move panel forward 25 mm (1.0 inch) then lift 51 to 76 mm (2.0 to 3.0 inch). Using 11/16 inch and 9/16 inch AF spanners, disconnect the copper pipe at the pressure gauge. Disconnect the transducer socket from the circuit board by carefully easing out the plug with a small screwdriver. Remove the two tach battery leads and lift out panel.Pressure Gauge
The glycerine filled gauge is connected to the block by a capillary tube. If this not working, clean tube with organic solvent and blow air through line.If the gauge is damaged, a replacement should be made. Ensure that the copper sealing ring is in good condition and the connection is securely tightened.Temperature
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Panel Plug on Circuit Board Temperature Signal Pins 1 and 2Earth Pin 5Flow Transducer Signal Pins 3 and 4To check the temperature reading on the display, connect a 10,000 ohm 1 percent resistor between pins 1 and 2. Switch selector switch to "TACH" or "INT" and check that the display reads 50.5 degrees C / 2 degrees C. Consult sales office for further information.Transducer
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TransducerTemperature Signal Pins 1 and 2Coil Pins 3 and 4Screen Pin 5Connect voltmeter (20,000 ohm/volt) between pins 1 and 2. Check that resistance is 38,000 ohms at 20° C (68.0 ° F) and 30,000 ohms at 30° C (86.0° F). Check that coil resistance is 4000 ohms between pins 3 and 4. If low resistance is obtained, check socket wiring.Turbine
If the turbine does not run free after being cleaned in solvent, the turbine bearing should be replaced. Carefully unscrew the turbine straighteners, remove the turbine rotor, and disassemble the turbine circlips. Replace the bearing and circlips, reassemble straighteners with Loctite type thread sealant.Transducer Adjustment
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Replace turbine, blow air into inlet port. Connect transducer plug to Voltmeter. Switch to A/C. Meter should read 1 to 2 V at maximum flow indication. If reading below 1/4 volt at minimum flow indication, adjust position of transducer. Loosen sleeve nut and carefully screw in transducer until the turbine slows to a stop and the voltage falls to zero. Reverse turn by 1/8 of a turn and retighten sleeve nut. Repeat voltmeter test and if not within voltage range replace transducer.Replacing Components
Display
Remove the four M3 nuts holding the circuit boards to the panel. Lift away circuit boards in order to gain access to the display. Lift out the display and replace with new display. The cutout in the dark edge of the display should face to the right-hand side when the circuit board is