HVAC
<<  Page 486 of 704  >>
HEAVY DUTY TRUCK & OFF-HIGHWAY EQUIPMENT
Procedures for R-12 to R-134a System Conversion
CAUTION: Always wear safety goggles when servicing a pressurized A/C system.
Make certain blower fan
STEP 1:
STEP 5:
speeds are working.
VISUAL
SYSTEM FLUSHING
Make certain heater control
INSPECTION
valve or blend door is in off
As R-134A and mineral oil
position when maximum
are not compatible, it is
Make certain engine is off.
A/C is selected.
necessary to flush any re-
Check for worn, broken or
sidual oil out. As a mechanic
leaking A/C hoses or other
STEP 3:
would have no way of telling
obvious leakage, broken or
how many ounces of oil
missing parts and note.
LEAK CHECK
remain, this also ensures
If visual inspection is O.K.,
With engine and A/C sys-
any oil overcharge doesn’t
proceed to Step 2.
tem off, check the system
occur, which would cause
for leaks with an electronic
STEP 2:
compressor slugging.
leak detector or tracer dye.
It is also necessary to flush
PERFORMANCE
If the system has little or no
out the A/C system if
refrigerant, sufficient R-12
CHECK
compressor or component
must be added to perform
Make certain engine is off.
failure has occurred. The
a correct leak test and to
Attach gauge and hose set
following flush procedures
determine if component
to A/C system on maxi-
are suggested for use with
problems exist.
mum setting and high-level
a pressured type flush gun
If no system leaks are
blower speed.
and A/C Flush.
found, proceed to Step 4.
Make certain compressor
Fill flush gun with 6 to 14 oz.
If leaks are found, take note
clutch is engaged.
of A/C Flush.
for later repair and proceed
Observe A/C outlet duct
Prepare A/C system for
to Step 4.
temperature and system
flushing by disconnect-
pressures. If o.k. proceed to
ing hoses from condenser,
STEP 4:
Step 3.
evaporator, compressor,
RECOVER R-12
If A/C outlet duct tempera-
accumulator or filter drier.
ture and gauge readings are
REFRIGERANT
Remove expansion valve or
not o.k. attempt to isolate
orifice tube from evaporator
It is unlawful to vent R-12
the problem.
or liquid line. Do not flush
refrigerant into the atmo-
Listed below are some
sphere. Recover R-12 with
these components. The
common areas to check:
a conventional recover/
accumulator or filter drier
Is the compressor belt
recycling machine accord-
should be replaced with
tight?
ing to EPA regulations and
a unit containing XH-7 or
Is condenser/ radiator fan
SAE procedures. Equipment
XH-9 desiccant.
working or fan clutch work-
should meet SAE J1990 and
Connect compressed air or
ing?
J2209 specifications.
nitrogen to flush gun con-
Is compressor clutch en-
Once the A/C system has all
tainer.
gaged (air gap between pul-
the R-12 removed, repairs
CAUTION: DO NOT EX-
ley and hub face to wide? Is
and service can be per-
CEED MANUFACTURER’S
clutch wire connected?
formed.
MAXIMUM ALLOWED SYS-
Check radiator coolant
TEM PRESSURE.
level.
Flush hoses, evaporator and
Check condenser condi-
condenser. Care should be
tion (use air to blow out any
taken when flushing con-
bugs, leaves, dirt or other
densers and evaporators
debris that might restrict
so that excessive flush is
airflow).
not left in the system. It is
Fast cycling might indicate
not advisable to flush the
low refrigerant or plugged
compressor as debris could
orifice tube or expansion
be lodged within oil chan-
valve.
nels, bearings, seals or valve
plates and reeds.