
Page 115
Timer Parameters
A/C Switch Fan On-Time
Description:
If the truck has a normally closed A/C High Pressure
switch installed and connected to the ECM, and the
ECM is wired to run the cooling fan, then the A/C Switch
Fan On-Time can be programmed to prevent excessive
cycling of the cooling fan clutch. This parameter has
no effect on any other Cooling Fan On condition, only
when the cooling fan is turned on by high A/C Pressure.
Programming the A/C Switch Fan On-Time to 0 (zero)
disables this feature and the ECM will not monitor this
input.
Open
Closed
On
Off
Low
Pressure
High
Pressure
Refrigerant
Pressure
A/C Pressure
Switch Contacts
Cooling Fan
A/C Pressure
Switch
Fan-On
Time
Available:
All electronically controlled on-highway engines
covered in this handbook
Range:
Range
Cat
DefaultMinimum Maximum
0 Seconds 600 Seconds 0 Seconds
Advantages:
The A/C Switch Fan On-Time can reduce the amount of
fan cycling and increase fan clutch life.
Recommendations:
✔ Caterpillar recommends a setting of 60 to 120
seconds with 134a refrigerant.
✔ Program the timer to 1 second if this input is
connected another system which is also providing
a time delay.