Air Conditioning High Pressure Switch

17.2.2 Slip Mode Operation will occur under the following conditions:

17.2.3 Brake Mode Operation (Fan OFF) will occur if engine rpm exceeds 2300 rpm or when all of the following conditions are met:

Slip Mode Operation for C-15 and C-16 Slip Mode Operation for C-10 and C-12

Coolant Sensor Temperature increasing > 194°F (90°C). Coolant Sensor Temperature increasing > 194°F (90°C).

NOTE: If the cooling fan is operating in Slip Mode the fan will continue to operate in Slip Mode until coolant sensor temperature is < 178°F (81°C).

Intake Air Sensor Temperature increasing > 127°F (53°C). NOTE: If the cooling fan is operating in Slip Mode the fan will continue to operate in Slip Mode until coolant sensor temperature is < 178°F (81°C).

Intake Air Sensor Temperature increasing > 127°F (53°C).

NOTE: If the cooling fan is operating in Slip Mode the fan will continue to operate in Slip Mode until intake air sensor temperature is < 34°F (1°C).

NOTE: If the cooling fan is operating in Slip Mode the fan will continue to operate in Slip Mode until intake air sensor temperature is < 34°F (1°C). *A/C High Pressure Switch Input is Open or ECM is Counting. *A/C High Pressure Switch Input is Open or ECM is Counting.

Brake Mode Operation for C-15 and C-16 Brake Mode Operation for C-10 and C-12

Coolant Sensor Temperature < 196°F (91°C). Coolant Sensor Temperature < 196°F (91°C).

NOTE: If the cooling fan is operating in Slip Mode the fan will not transition to Brake Mode until the coolant sensor temperature decreases to < 178°F (81°C).

NOTE: If the cooling fan is operating in Slip Mode the fan will not transition to Brake Mode until the coolant sensor temperature decreases to < 178°F (81°C). The fan has been ON for at least 20 seconds. The fan has been ON for at least 20 seconds.

Intake Manifold Air Temperature < 129°F (54°C). Intake Manifold Air Temperature < 129°F (54°C).

NOTE: If the cooling fan is operating in Slip Mode the fan will not transition to Brake Mode until the coolant sensor temperature decreases to < 34°F (1°C). NOTE: If the cooling fan is operating in Slip Mode the fan will not transition to Brake Mode until the coolant sensor temperature decreases to < 34°F (1°C).

Engine Retarder ON Strategy is not Active. Engine Retarder ON Strategy is not Active.

A/C High Pressure Switch not Active. A/C High Pressure Switch not Active.

PTO On/Off Switch in OFF Position. PTO On/Off Switch in OFF Position.

Manual Fan Override Switch in OFF position Manual Fan Override Switch in OFF position

17.3 Air Conditioning High Pressure Switch

Input #11 to the ECM is available for connection of a normally closed high pressure A/C switch. The ECM has a timer available to prevent excessive cycling of the cooling fan clutch due to successive cycling of the A/C switch input. The timer is programmable from 0 to 600 seconds, with 0 seconds indicating the feature is OFF (the default). Typical programming is 30 seconds, with 1 second recommended for systems connecting this input to other controls with their own built in timers.

HighPress.

LowPress.

Refrigerant Pressure

SwitchOpen

SwitchClosed

FanOn

FanOff

A/CPressure SwitchCircuit

CoolingFan

A/C Fan Switch On Time

Output#5On

Output#5Off

Output#5

Output#4On

Output#4Off

*Output #4

*Output #4 only used when Fan Control Type is programmed to Three Speed Fan

Figure 33 - A/C High Pressure Switch Operation

OEM provided and installed components required: 1) Normally closed high pressure A/C switch. 2) Cooling fan connection to Output #5, and Output #4 (if Fan Control Type is programmed to On-Off or Three Speed Fan). Customer Parameter programming required: 1) Fan Control Type programmed to On-Off or Three Speed Fan. 2) A/C Pressure Switch Fan-On Time programmed in the 1 - 600 second range (0 = disabled).

17.3.1 A/C High Pressure Switch Operation

This switch must be a normally closed switch, opening when the refrigerant pressure exceeds the desired level. The ECM input is monitored only if the Customer Programmable Parameter for A/C Pressure Fan On Time is programmed in the 1-600 second range. Figure 33 illustrates the fan operation due to this input. The A/C Pressure Switch Fan-On Time is programmable from 0 to 600 seconds. If the Parameter is at 0 seconds, the ECM will not respond to the input. Figure 33 - “A/C High Pressure Switch Operation” indicates the ECM A/C High Pressure Switch operation.