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375 Caterpillar Standard and Aftercooled/Filtered Operator’s Manual and Parts List
SECTION 2
AFTERCOOLED AND FILTERED 2.12 
AIR SYSTEM, FUNCTIONAL 
DESCRIPTION
Refer to Figure 2-3. The purpose of the aftercooled system 
is to operate the air compressor in conditions when 
compressed air temperature is required to be within 20° to 
25°F (13° to 17°C) of the ambient temperature. 
A selector valve is provided on all aftercooled 
compressors. Choosing the aftercooled air completely 
forces the airow from the receiver tank to the aftercooler. 
The ambient air which is drawn through the aftercooler by 
the engine fan, cools the compressed air as it passes 
through the aftercooler core. Cooled air enters the 
moisture separator where condensation is removed from 
the cooler air and discharged. This condensate does 
carry some oil and it should be disposed of properly 
in accordance with local regulations. 
From the moisture separator the air enters the (optional) 
rst stage lter. Particles and additional water are removed 
from the rst stage lter. The condensate should be 
drained and stored in a suitable container. From the 
rst stage lter, the air enters the (optional) second stage 
lter. This lter removes smaller particles and any 
additional water. The condensate should be drained 
and stored in a suitable container. Upon compressor 
shutdown, the lters will drain to clear the condensate from 
the system. This will prevent freezing in cold conditions.
NOTE
The aftercooler system should 
not be operated when the ambient 
temperature is below 32°F (0°C). To 
operate in the non-aftercooled mode 
close the aftercooler selector valve 
completely.