D5R2 and D6R2 Track-Type Tractors HVAC, Heating System Caterpillar

The following problem solving section is provided for identifying and correcting problems that may occur in the heating system. Several problems can have the same system condition (symptom) or similar system conditions. Before you start the procedure in order to correct the problems, evaluate the performance using the Testing and Adjusting, UENR4125, "Heater Performance –Test". Be complete in the diagnosis of the problem. Repair the components or replace any damaged component if the components are faulty during the inspection.

Symptom: There is little or no warm air that is flowing to the cab when the heater control knob is set to maximum heat.

Possible Cause 1

The blower motor is not working.

1. Inspect the circuit breaker or the fuse panel in order to ensure that there is no open circuit.

2. Visually inspect the wire harnesses in order to check for any broken wires or missing connectors. Use the electrical schematic for the respective machine to ensure proper connections.

3. Check the fan blade in order to make sure that the fan blade is not blocked or seized.

4. Check for the proper function of the fan switch at each setting. The blower motor should engage at all settings and temperatures.

Possible Cause 2

There is a leak that is present in the system.

1. Check the hose clamps making sure that the clamps are present and tightened to the correct torque value that is shown on the drawing.

2. Check the heater coil for any visible cracks or signs of a leak.

3. Check the water valve in order to make sure that the water valve is properly installed and operational.

Possible Cause 3

The inlet/outlet ports for the engine cooling system are closed.

1. Inspect the valves that connect the heater hoses to the engine block.

2. Make sure that the valves are adjusted so that the valves are fully open.

Possible Cause 4

The hose that is connecting the system together is kinked or blocked.

1. Check for blockage or bends in the hoses. Blockages and bends in the heater hoses restrict the flow of coolant and the blockages reduce the performance of the entire heating system.

2. Replace any hoses that appear to be restricting the flow of coolant.

Possible Cause 5

There is a failure with the device for the heater control.

1. Determine the type of controlling device that is used on the machine.

2. If there is a water valve that is present, continue to Step 3. If there is a blend door that is present, continue to Step 6.

3. Inspect the water valve for any signs of damage.

4. Check the water valve making sure that the valve opens completely when the temperature control knob is set to maximum heat.

5. If the water valve fails to open or the water valve fails to close, move to "Possible Cause 6".

6. Inspect the blend door.

7. Check the blend door for any damage.

8. Make sure that the insulation is still attached to the blend door.

9. Make sure that the actuator is connected to the blend door.

10. Check the blend door making sure that the door opens completely when the temperature control knob is set to maximum heat.

Possible Cause 6

There is a failure with the cable for the water valve or the potentiometer.

1. Determine the type of control for the water valve that is being used on the machine.

2. If there is a cable that is attached to the water valve, continue to Step 3. If the machine has a built-in potentiometer, continue to Step 5.

3. Check the machine in order to make sure that the cable is attached to the water valve handle.

4. Check the water valve making sure that the valve opens completely when the temperature control knob is moved to maximum heat.

5. Check the machine in order to make sure that the potentiometer is attached to the wire harness within the dash of the cab.

6. Check the water valve making sure that the valve opens completely when the temperature control knob is moved to maximum heat.

Symptom: The heat that is within the cab is uncontrollable.

Possible Cause 1

The water valve is installed incorrectly or backward.

1. If the machine is equipped with a water valve control, check the valve making sure that the valve is installed properly.

2. Some water valves are manufactured so that there is an arrow that shows the flow direction on the side of the valve body. Make sure that the arrow is pointed toward the line that leads to the heater coil.

3. If the machine is equipped with a cable driven water valve, make sure that the cable is not wrapped around the valve, or the frame of the machine.

4. If the machine is equipped with an electronically driven water valve, make sure that the actuator is attached securely to the water valve.

Possible Cause 2

There is an electrical failure with the control panel.

1. Inspect the control panel in order to make sure that the control panel is receiving power when the machine is turned on.

2. Check in order to make sure that the wire harness is connected to the control panel.

3. Inspect the wire harness for any breakage or exposed wires.

4. Inspect the circuit breaker or the fuses in order to ensure that there is not an open circuit.

Possible Cause 3

There is a failure with the cable for the water valve or the potentiometer.

1. Determine the type of water valve control that is present on the machine.

2. If there is a cable that is attached to the water valve, continue to Step 3. If the machine has a built-in potentiometer, continue to Step 5.

3. Check in order to make sure that the cable is attached to the water valve handle.

4. Check in order to make sure that the water valve opens completely when the temperature control knob is moved to the position of maximum heat.

5. Check in order to make sure that the potentiometer is attached to the wire harness within the dash of the cab.

6. Check in order to make sure that the water valve opens completely when the temperature control knob is moved to the position of maximum heat.

Symptom: There is a coolant smell that is present within the cab.

Possible Cause 1

There is a leak that is present at the hose or the hose clamps.

1. Inspect the connections between the heater coil and the heater hoses.

2. Check the hoses for cuts.

3. Check in order to make sure that the hose clamps are tightened to the proper torques that are shown on the dimension drawings.

Possible Cause 2

There is a leak that is present at the heater coil.

1. Inspect the heater coil in order to determine if there are any visible cracks or holes in the tubing.

2. Check in order to make sure that the hose clamps are tightened to the proper torques.

Possible Cause 3

There is a leak that is present at the water valve.

1. Inspect the water valve for any damage.

2. Check in order to make sure that the hose clamps are tightened to the proper torques.

3. If the water valve passes both these initial tests, refer to the Troubleshooting, UENR4125, "Machine Preparation For Testing and Adjusting".

Symptom: There is no flow of air to the operators compartment. The evaporator blower motors do not operate when the fan switch is activated.

Probable Cause 1

There is an open circuit.

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	g03417164
Typical Blower Control Switch for analog signal is on the left side.

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Illustration 2	g03419432
Coil type wire resistor

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Illustration 3	g03419433
Ceramic wire

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Illustration 4	g03417195
Typical Resistor Controlled Blower Speed Refer to specific machine schematic for type

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Illustration 5	g03417200

3. Each resistor terminal combination will change the blower speed. HVAC Panel Pin5 (Blower Low) will connect to Blower Resistor Pin 1 (Low Speed). Refer to Illustration 5 shown above.

4. Blower switch should have continuity for each fan speed. Resistor ohm value should decrease from Low to High Speed. Refer to Illustration 5, and electrical schematic section for additional information for the machine.

Probable Cause 2

There is a blockage in the fan blades.

1. Check for blockages at the fan blades.

Probable Cause 3

The motor has failed.

1. Make necessary repairs or replace motors and components.

2. After a new motor or blower wheel is installed, inspect operation for the correct rotation.