MCC 68AC430-100, Operation & Service Manual

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4--6
©
2012 Mobile Climate Control T-353 Rev. 01/2013
c. Connect manifold gauge set and reclaimer to the
filter drier service valve access ports and reclaim
any refrigerant contained in the filter drier.
d. Place a new filter-drier near the unit for immediate
installation.
WARNING
The filter-drier may contain liquid refrig ­
erant. Slowly loosen the connecting nuts
and avoid contact with exposed skin or
eyes.
e. Using two open end wrenches, slowly crack open
the connecting nuts on each side of the filter-drier
assembly. Remove the filter-drier assembly.
f. Remove seal caps from the new filter-drier. Apply
a light coat of mineral oil to the filter-drier connec ­
tions.
g. Assemble the new filter-drier to lines ensuring that
the arrow on the body of the filter-drier points in
the direction of the refrigerant flow (refrigerant
flows from the receiver to the evaporator). Finger
tighten the connecting nuts.
h. Tighten filter-drier connecting nuts using two
open end wrenches.
i. Connect vacuum pump to manifold gauge set and
evacuate filter to 500 microns. Close gauge valve,
vacuum pump valve, and stop vacuum pump.
j. Backseat (fully close) both service valve ports and
replace valve caps.
k. Remove Gauges.
4.11 SERVICING THE HEAT VALVE
The heat valve (Figure 4-5) requires no maintenance
unless a malfunction to the internal parts or coil
occurs. This may be caused by foreign material such
as: dirt, scale, or sludge in the coolant system, or
improper voltage to the coil.
NOTE
The OEM supplied heating (hot water) Sole ­
noid Valve is normally located outside of the
AC430 rooftop air conditioning system.
There are only three possible valve malfunctions: coil
burnout, failure to open, or failure to close.
Coil burnout may be caused by the following:
1. Improper voltage
2. Continuous over-voltage, more than 10% or Un ­
der-voltage of more than 15%.
3. Incomplete magnetic circuit due to the omission
of the coil housing or plunger.
4. Mechanical interference with movement of plung ­
er which may be caused by a deformed enclosing
tube.
Failure to open may be caused by the following:
1.Coil burned out or an open circuit to coil connec ­
tions.
2. Improper voltage.
3. Torn diaphragm.
4. Defective plunger or deformed valve body assem
­
bly.
Failure to close may be caused by the following:
1. Defective plunger or deformed valve body as ­
sembly.
2. Foreign material in the valve.
3. Torn diaphragm.
4.11.1 Coil Replacement
a. It is not necessary to drain the coolant from the
system.
b. Place main battery disconnect switch in OFF posi ­
tion and lock.
c. Disconnect wire leads to coil.
d. Remove coil retaining screw and nameplate.
e. Lift burned-out coil from enclosing tube and re
­
place.
f. Connect wire leads and test operation.
4.11.2 Internal Part Replacement
a. Disconnect system from bus battery.
b. Open the vent fitting at the top of the outlet head
­
er of the heater coil.
c. Drain coil by opening the drain-cock on the inlet
tube.
d. Disassemble valve and replace defective parts.
e. Assemble valve, refill and bleed coolant lines.
4.11.3 Replace Entire Valve
a. Disconnect system from bus battery.
b. Drain coolant from lines as previously described
and disconnect hoses to valve .
c. Disconnect wire leads to coil.
d. Remove valve assembly from bracket.
e. Install new valve and re-connect hoses. It is not
necessary to disassemble the valve when installing.