Carrier AC350 - 5.15 Replacing Return Air Filters; 5.16 Thermostatic Expansion Valve

T -304
5--8
04/08
5.15 REPLACING RETURN AIR FILTERS
The return air filters are located behind the return air
grill, inside the vehicle.
The filters should be checked for cleanliness
periodically depending on operating conditions. A dirty
filter will restrict air flow over the evaporator coil which
may cause insufficient cooling or heating and possible
frost buildup on the coil. To remove the filters, do the
following.
a. Insure air conditioning system is in the off position.
b. Remove the return air grille with the filter--diffuser as-
sembly, by turning the six 1/4 turn fasteners counter-
clockwise.
Return Air F ilter
Composit Frame
Figure 5--9 Return Air Grill Assembly
With Air Filter Showing
c. Remove diffuser from the bus composit frame.
Diffuser
Return Air F ilter
Figure 5--10 Diffuser and Filter Element
d. Remove and replace the filter element.
e. Center diffuser on filter element.
f. Pullfilterelementapproximately1/4inchoverendsof
the diffuser.
Composit Frame
Diffuser
Air Filter
Figure 5--11
Filter, Diffuser and Composit Frame
g. Placefilter anddiffuserintocompositframe, withfilter
element down (See Figure 5--11).
Captive 1/4 Fastners
Figure 5--12 Return Air Grill Assembly
With Diffuser And Composit Frame Showing
h. Insert filter--diffuser assemblyintocomposit frameon
bus with the six captive 1/4 fasteners. (See
Figure 5--12)
i. Lock the six captive 1/4 turns in place by rotating
clockwise.
5.16 THERMOSTATIC EXPANSION VALVE
The thermostat expansion valve (Figure 5--13) is an
automatic device which maintains constant superheat
of the refrigerant gas leaving the evaporator regardless
of suction pressure. The valve functions are: (a)
automatic control of refrigerant flow to match the
evaporator load and (b) prevention of liquid refrigerant
entering the compressor . Unless the valve is defective,
it seldom requires any maintenance.