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© 2012 Mobile Climate Control T-299 Rev. 08/2012
SECTION 3
TROUBLESHOOTING
3.1 INSUFFICIENT OR NO COOLING
3.1.1 Preliminary Checks
Make certain that the evaporator filters are not
clogged with dirt. Check to make certain that all
vehicle body openings are air tight. Check the
adjustment and condition of the compressor drive
belt (s); adjust or replace as necessary. Refer to
Sectio n 4, paragraph 4.12 for complete drive belt
installation and maintenance pro cedu res.
3.1.2 Checking System Air Output
If the evaporator air flow appears less than normal,
check the evaporator filter and coil for dirt and
obstructions. Clean where necessary. Check the
blower assembly for proper operation. Current draw
will vary as to evaporator, speed setting and voltage.
See Table 3-1, Table 3-2 or Table 3-3 for
approximate evaporator current draw. If the current
drawn by the motor is not to specifications, replace
the motor.
3.1.3 Check The Sight Glass For Bubbles
If the preceding steps do not rem edy the prob lem,
check the sight glass for bubbles. Run the vehicle
engine at high idle (approximately 1200 RPM) while
maintaining a minimum discharge pressure of 150
psig. The thermostatic switch should be positioned
for maximum cooling.
Bubbles in the sight glass may indicate an
undercharge of refrigerant and/or a restrictio n in the
liquid line. If the ch arge is low, check the system for
leaks; repair if necessary and charge the system with
the proper amount o f refrigerant.
NOTE
Under certain ambient conditions a few
bubbles may appear in the sight glass. Refer
to Section 4, Table 4-5 to determine if sys
tem has correct charge.
No bubbles in the sight glass will indicate either a full
charge or a complete loss of refrigerant. To
determine if there is refrigerant in t he system, run the
vehicleengine at high idle (approximately 1200 RPM)
with the thermostatic switch positioned for
maximum cooling. Allow system to stabilize, then
shut system down while observing the sight glass. If
bubbles begin to appear, the system has a refrigerant
charge. If no bubbles appear, system is without
refrigerant.
A restriction in the liquid line can be found by feeling
the liquid line. Any portion that is cold to the touch
or that frosts up is restricting the refrigerant flow.
3.1.4 Compressor Amp Draw
Split System Compressor clutch coils typically draw 2
to 3 Amps.
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