Air Inlet Heater Caterpillar

Air Inlet Heater

Usage:

ENGINES3126 (8NM4196-4256, 1ZJ1-Up) MARINE ENGINES

Problem:

There have been reports of the Air Inlet Heater remaining "ON" or continuously cycling "ON" and "OFF". This could draw the battery voltage down on the boat. Investigation indicates that the 112-5475 Water Temperature Switch is not operating correctly. This switch is supposed to shut off the air inlet heater when the engine coolant temperature reaches 49(C (120(F). This switch is installed on the engine before it is cleaned and painted. The protective cap on the switch is not tight enough to prevent water and paint from entering the switch and causing the switch to "short out".

Solution:

Use an ohmmeter to check the electrical continuity of the of the 112-5475 Water Temperature Switch. When the engine coolant temperature is above 49 ± 4°C (120 ± 7°F), the switch should be "open circuit". When the engine coolant temperature is below 35 ± 4°C (95 ± 7°F), the switch should be "closed circuit". If the 112-5475 Water Temperature Switch is not operating correctly, replace the switch. This switch is located on the top of the engine water pump.

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