Cooling Fan

17.0 Cooling Fan

The ECM provides a cooling fan disable signal (ECM output = high for fan OFF) for On/Off control of the cooling system fan based on coolant temperature, engine retarder operation, engine rpm, and intake manifold air temperature. Optional control based on an OEM installed air conditioning high pressure switch or a manual Fan Override switch can also be selected. The parameter Fan Control Type determines how the ECM controls a fan.The Fan Control Type programmable options are On-Off, Three Speed Fan and NONE (default). Program this parameter to None if the ECM is not connected to the Cooling Fan circuit. This will aid the service technician for troubleshooting purposes if correctly programmed. To prevent unnecessary cooling fan cycling due to reduced voltage levels during engine cranking, the ECM turns the output(s) OFF (fan ON). Because an electrical open circuit is the most likely failure mode, Caterpillar recommends a normally open circuit(s).

17.0.1 Output #5 Electrical Specifications

Electrical characteristics of the fan control high side driver is as follows:

Minimum “ON” Output Voltage Maximum “ON” Output Voltage Maximum Current Draw OFF State

Battery - 2.0 Volts DC Battery 1.5 A (12 V or 24 V) High Impedance

The drivers are intended for connection to the cooling fan solenoids. Caterpillar recommends transient suppression be used on the inductive load in addition to the ECM’s internal protection. Connection for these output:

Terminal Description ECM Terminal Assignment

Output #4 Terminal 13 Output #5 Terminal 11

Wiring Diagram 34 - On-Off Cooling Fan Circuit

Wiring Diagram 35 - Three Speed Cooling Fan Circuit