14M3 Motor Grader Electrical System Troubleshooting Caterpillar

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Personal injury can result from contact with refrigerant. This system is under pressure at all times, even if the engine is not running. Heat should never be applied to a charged system. Contact with refrigerant can cause frost bite. Keep face and hands away to help prevent injury. Protective goggles must always be worn when refrigerant lines are opened, even if the gauges indicate the system is empty of refrigerant. Always use caution when a fitting is removed. Slowly loosen the fitting. If the system is still under pressure, evacuate the system recovering the refrigerant before removing the fitting. Personal injury or death can result from inhaling refrigerant through a lit cigarette. Inhaling air conditioner refrigerant gas through a lit cigarette or other smoking method or inhaling fumes released from a flame contacting air conditioner refrigerant gas, can cause bodily harm or death. Do not smoke when servicing air conditioners or wherever refrigerant gas may be present. Before any checks of the air conditioning and heating system are made, move the machine to a smooth horizontal surface. Lower all implements to the ground. Make sure the transmission is in neutral or park and that the parking brake is engaged. Keep all other personnel away from the machine or where they can be seen.

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Personal injury can result from hot coolant. Any contact with hot coolant or with steam can cause severe burns. Allow cooling system components to cool before the cooling system is drained.

Heating System

To conduct a performance check of the heating system, perform the following procedure.

1. Run the engine at 1000 rpm.

2. Adjust the temperature control knob to the setting for maximum heating.

3. Put the fan switch in the HIGH position on heat.

4. When engine coolant is at normal operating temperature, the air that is flowing from the louvers (air ducts) should be warm.

   If the temperature of the air that is flowing is not warm within 10 minutes of operation, refer to "Problem 2" section.

Problem 1

There is little warm air flow or no warm air flow when the heater control knob is set for maximum heating.

1. Perform the following procedure:

   1. Check the engine coolant temperature. The temperature of the coolant must be at normal operating range.

   2. The heater control valve must be functioning properly. Check for the correct linkage adjustment from the temperature control lever to the heater control valve. The heater control valve must open completely when the temperature control knob is set for maximum heating.

   3. Check for blockage and check for bends in the heater hoses. Blockages and bends in the heater hoses would stop the flow of coolant through the system.

   4. Inspect the petcocks that connect the heater hoses to the engine block. Make sure that the petcocks are adjusted so that the petcocks are fully open.

2. Make repairs to the components or replace any damaged component.

Electrical System

Problem 2

The operator compartment has no air flow. The evaporator blower motors do not operate when the fan switch is activated.

1. Perform the following procedure:

   1. Inspect the circuit breaker or inspect the fuses for an open circuit.

   2. Check for the proper function of the control panel at each speed setting. The evaporator blower motor must run at each setting. The evaporator blower motor should be operating in the cold mode and in the heating mode.
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   Illustration 1	g03843320
   Typical blower control switch for analog signal is on the left side

2. If necessary, make repairs or replace components.

   1. Check for the proper function of the control panel at each speed setting.

Perform this test with the key on. Use a 5P-7277 Voltage Tester or use a 257-9140 Digital Multimeter and connect the negative probe to the pin 7 wire on the control panel using a 7X-1710 Multimeter Probe7x-1710 wire assembly or equivalent. Check the supply voltage first by connecting the positive probe to the pin 1 wire using a 7X-1710 Multimeter Probe wire assembly or equivalent. If the system voltage is not measured, do not perform any of the other tests below until that is repaired. Select the blower switch to the low speed and connect the positive probe to pin 5 using a 7X-1710 Multimeter Probe wire assembly or equivalent and record the voltage. For a properly working control panel, the voltage should be the same as the system voltage. Repeat for all speeds. Replace the panel if any of the voltages are not present during the test.

If the panel passes the test, then refer to the machine electrical schematic and check for voltage to the motor and resistor.

Test Procedure for Testing Electrical Components in the Air Conditioning System

The air conditioning systems on Cat machines use pressure switches to protect the air conditioning system. Some air conditioning systems on Cat machines use pressure switches and on delay timer assembly for the refrigerant compressor to protect the air conditioning system. Arc suppressors protect other electrical components in the air conditioning system. Arc suppressors are applied to discharge electrical inductance when the compressor disengages. Failure of the arc suppressor can affect the reliability of the pressure switch. Failure of the arc suppressor may cause failure of the pressure switch.

The following procedures are for the testing of the on delay timer assembly, pressure switches, and components of the arc suppressor.

Pressure Switch Tests

Test Procedure for 114-5333 Pressure Switch / 355-3148 Pressure Switch and 114-5334 Pressure Switch (NORMALLY OPEN)

Pressure switches are used to protect the a/c compressor. The two most commonly used pressure switches are the 114-5333 Pressure Switch / 355-3148 Pressure Switch and the 114-5334 Pressure Switch. The only difference between the two switches is the connector. Only one of these switches is used per machine. The high pressure and low-pressure switches have three possible switch positions which are given below:

OPEN - System pressure is low.

CLOSED - System pressure is correct.

OPEN - System pressure is high.

The two OPEN positions of the pressure switch protect the air conditioning system. The OPEN position prevents the compressor from actuating when potentially harmful pressures exist in the system. The CLOSED position is the normal operating switch position. The following table contains the logic for the pressure switches:

Illustration 2	g00651406

Use the following procedures to test the pressure switch:

1. Disconnect the pressure switch from the machine harness.

2. Connect the 257-9140 Digital Multimeter to the two connector pins. Set the multimeter to the OHMS test mode.

3. Measure the resistance of the pressure switch.

4. If the system pressure is between 275 kPa (40 psi) and 1750 kPa (254 psi), the multimeter will display a value less than 1 ohm.

5. If the resistance that is displayed is a value of OL (high resistance), and the system pressure is within acceptable limits, replace the pressure switch.

6. When the pressure switch fails, test the arc suppressor for proper operation.

7. If the pressure switch is removed, make sure that the wires on the new pressure switch are tie-wrapped. Securing the pressure switch prevents damage that may be caused by vibration.

Note: The multimeter may display OL if the contacts on the pressure switch are dirty. The contacts on the pressure switch can become dirty if the arc suppressor is no longer functioning.

Note: The multimeter will display OL if the pressure switch is not threaded into the air conditioning system.

149-6371 Low-Pressure Switch (NORMALLY OPEN)

Illustration 3	g00651452

Use the following procedures to test the pressure switch:

1. Disconnect the pressure switch from the machine harness.

2. Connect the 257-9140 Digital Multimeter to the two connector pins. Set the multimeter to the OHMS test mode.

3. Measure the resistance of the pressure switch.

4. If the system pressure is above 103 ± 14 kPa (15 ± 2 psi), the multimeter will display less than 1 ohm.

5. If the measured resistance displays a value of OL (high resistance), and the system pressure is not below the acceptable limit, replace the pressure switch.

6. When the pressure switch fails, test the arc suppressor for proper operation.

7. If the pressure switch is removed, make sure that the wires on the new pressure switch are tie-wrapped. Securing the pressure switch prevents damage that may be caused by vibration.

Note: The multimeter may display OL if the contacts on the pressure switch are dirty. The contacts on the pressure switch can become dirty if the arc suppressor is no longer functioning.

Note: The multimeter will display OL if the pressure switch is not threaded into the air conditioning system.

Test Procedures for Arc Suppressors:

189-3158 Arc Suppressor

Illustration 4	g00651378
106-8704 Arc Suppressor

1. Place the multimeter in the DIODE test mode.

2. Place the red probe in the red terminal (positive terminal) of the multimeter.

3. Place the black probe in the black terminal (negative terminal) of the multimeter.

4. Place the red probe on Pin 2 of the connector on the arc suppressor. Place the black probe on Pin 1 of the connector.

5. The multimeter should display a value between 0.5 VDC and 1.0 VDC.

6. Place the red probe on Pin 1 of the connector on the arc suppressor. Place the black probe on Pin 2 of the connector on the arc suppressor.

7. The multimeter should display OL.

8. If the above conditions do not exist, the component should be considered faulty. The component will not provide adequate protection if the above conditions do not exist.

9. Replace the component if the component has failed.

Correct Mounting of Arc Suppressors

Certain arc suppressors may experience failure of the wire leads due to vibration if the arc suppressor is not properly supported.

Use a 2U-4497 Strap to tie-wrap the arc suppressor. Securely tie-wrap the arc suppressor to a stationary support to prevent any motion of the body of the arc suppressor. Also, the connectors on both ends of the arc suppressor should be secured.

A suitable bracket for supporting an arc suppressor is the 116-6100 Plate. The addition of a 9R-2926 Plate should permit the mounting of the 116-6100 Plate around obstacles. Use the 9R-2926 Plate if the 116-6100 Plate cannot be installed directly in an existing application.

The Sure Seal connectors on the 3E-9169 Arc Suppressor and the 105-8827 Arc Suppressor should be secured with two 9G-9150 Clips to prevent movement of the connectors relative to the body of the arc suppressor. The DT connectors on the 130-0956 Arc Suppressor and 130-8134 Arc Suppressor should be secured with two 9U-2297 Clips. The clips should be bolted through the slotted holes on the 116-6100 Plate.

The 106-8704 Arc Suppressor is an integral arc suppressor. The integral arc suppressor can be found on the newer machines. The 106-8704 Arc Suppressor is lighter than the other arc suppressors. The 106-8704 Arc Suppressor can be strapped directly to the wiring harnesses that are connected to the arc suppressor.