307D, 311D, 312D, 313D, 315D, 318D, 319D, 320D, 323D, 324D, 325D, 326D, 328D, 329D, 330D, 336D, 340D, 345D, 349D, 374D, 390D and M325D Excavators Air Conditioning and Heating Heating System Troubleshooting Caterpillar


Heating System Troubleshooting
`
1.1. Poor Heating
2.2. Air flow is short
3.2. The blower motor rotates
4.3. Diagnostics
5.2. The blower motor does not rotate
6.3. Diagnostics
7.2. Normal air flow
8.3. Diagnostics
9.2. Air Outlet
10.3. Diagnostics
11.2. Air Inlet
12.3. Diagnostics
13.1. Specifications

Poor Heating

If the air flow is normal, see "Normal air flow". If the air flow is short, see "Air flow is short". If the changeover for the discharge is poor, see "Air Outlet". If the fresh air or recirculation is poor, see "Diagnostics".

Air flow is short

If the blower motor rotates, refer to "The blower motor rotates". If the blower motor does not rotate, see "The blower motor does not rotate".

The blower motor rotates

Diagnostics

  1. If the rotation is correct, see steps 2, 3, 4, 5, 6, and 8. If the rotation is slow, see steps 9, 10, 11, and 12.

  2. If the recirculation filter is clogged, clean the filter.

  3. If the fresh air filter is clogged, clean the filter.

  4. If an obstacle is logged at the inlet port, remove the obstacle.

  5. If the blower motor is distorted or broken, replace the blower motor.

  6. If the evaporator is frosted and there is voltage that is applied to the magnetic clutch, see 7. If the evaporator is frosted and there is no voltage that is applied to the magnetic clutch, the magnetic clutch is poor. Replace the magnetic clutch.

  7. Check the clutch circuit. If necessary, replace the clutch relay. Check the wiring of the frost sensor for a short. If necessary, repair the wiring. Check the characteristics of the frost sensor. If necessary, replace the frost sensor. Check the gap between the frost sensor and the evaporator. If necessary, adjust the distance for the gap. See "Specifications".

  8. If there is debris on the evaporator surface, clean the surface.

  9. If power voltage drops, check the battery or check the charging surface.

  10. If there is poor contact with the battery terminal, repair the terminal.

  11. If the blower motor is poor, replace the motor.

  12. If the blower high relay is poor, replace the relay.

The blower motor does not rotate

Diagnostics

  1. If the blower motor rotates only in the HI speed, see step 2. If the blower motor does not rotate in the HI, or Lo speeds, see steps 3, 4, 5, 6, 7, 8, and 9.

  2. If the resistor has an open circuit, replace the resistor.

  3. If a fuse has an open circuit, repair the fuse.

  4. If the power up relay of the vehicle is poor, replace the relay.

  5. If the blower motor is poor, replace the motor.

  6. If the blower motor is in contact with the case, repair the motor.

  7. If the blower switch is poor, replace the switch.

  8. If the body ground is poor, repair the ground.

  9. If the wiring is poor, repair the wiring.

  10. If the power transistor is poor, replace the transistor.

Normal air flow

Diagnostics

  1. If the temperature of the water is low, wait for the temperature of the water to increase. If the water temperature is normal, see steps 2, 3, 4, 5, and 6. If the LED that is used in order to adjust the temperature is operating normally, see steps 7 and 8. If the LED that is used in order to adjust the temperature is not operating normally, see steps 9 and 10.

  2. If air is in the circuit, remove the air.

  3. If the pipe is clogged, repair the pipe. If the pipe is bent, replace the pipe.

  4. The outside temperature is extremely low.

  5. The engine coolant level is low. Refill to the correct level.

  6. The heater core is faulty. Replace the heater core.

  7. The link for the adjustment of the temperature is not engaged. Engage the link.

  8. Foreign material is an obstruction. Remove the foreign material.

  9. The wiring is faulty. There is an open circuit or a disconnected connector.

  10. The actuator is faulty. Replace the actuator.

Air Outlet

Diagnostics

  1. If the actuator for the air outlet rotates normally, see steps 2 and 3. If the actuator for the air outlet does not rotate normally, see steps 4 and 4.

  2. If the link is disengaged, engage the link.

  3. If foreign material is present, remove the foreign material.

  4. The wiring is faulty. There is an open circuit or a disconnected connector.

  5. The actuator is faulty. Replace the actuator.

Air Inlet

Diagnostics

  1. If the actuator rotates normally, see steps 2 and 3. If the actuator for the air inlet does not operate normally, see steps 4 and 5.

  2. If the link is disengaged, engage the link.

  3. If foreign material is present, remove the foreign material.

  4. The wiring is faulty. There is an open circuit or a disconnected connector.

  5. The actuator is faulty. Replace the actuator.

Specifications

Check the distance of the gap between the frost sensor and the evaporator. ... 12 to 5 mm (0.472 to 0.197 inch)

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