Chevrolet 70 1969 Series, Shop Manual

Page: 82 / 913

C A B A N D BO DY M O U N T IN G S 1-55
INSUFFICIENT COOLING DIAGNOSIS CHART
X
C H E C K AIR F L O W
r
N O R M A L AIR F L O W
N O O R L O W AIR F L O W
Inspect system for visual de-
fects. Check aii^ temperature. Check blower operation.
H IG H AIR
N O R M A L AIR
AIR T E M P E R A T U R E
T E M P E R A T U R E
i -
T E M P E R A T U R E
VARIES
Check sight glass. Check for air leaks at cab doors,
windows, cowl, or unit drain hose.
If 7 F. variation at nozzle exist,
replace suction throttling valve.
See Note "A
_ L
.
B L O W E R N O T
OP E R A T IN G
N O R M A L B L O W E R
O P E R A T IO N
Check for blown fuse, defective blower
switch,
broken wire, loose ground
wire, defective blower motor.
B L O C K E D
E V A P O R A T O R
Check for loose hoses, restriction or
leakage in air ducts, partially closed air
outlet valve or clogged evaporator core.
If iced, check for low evaporator pressure.
Adjust suction throttling valve. If dirty,
remove using vacuum cleaner hose.
N O F O A M IN G
FO A M IN G
Check evaporator pressure.
System is probably low on refrigerant. Check for
leaks, repair and add refrigerant. If foaming still
occurs check for restriction in refrigerant system
between condenser and sight glass. See Note " C ."
N O R M A L
L O W HIGH
E V A P O R A T O R PRESSURE
E V A P O R A T O R PRESSURE E V A P O R A T O R PRESSURE
Check - compressor
discharge pressure.
C O M P R E S S O R HIGH
D IS C H A R G E PRESSURE
Check for air in system, excess
refrigerant, restriction in con­
denser refrigerant tubes or air
fins. See Note ”B."
If ice is blocking evaporator, adjust
suction throttling valve. If cooling
remains low, follow diagnosis under
"Normal Evaporator Pressure." If
valve does not respond to adjust­
ment, hoses to and from valve and
suction hose may be restricted or
valve may be defective.
Adjust to normal
evaporator pressure.
If unable to adjust-
C O M P R E S S O R L O W
D IS C H A R G E PRESSURE
RESPONDS T O
A D J U S T M E N T
Check for low refrigerant, restric­
tion in liquid line, plugged or de­
fective expansion valve, or defective
compressor or suction throttling
valve. See Note " C ."
N O RESPONSE
T O A D J U S T M E N T
Repair or replace suc­
tion
throttling valve.
N O R M A L
HIGH
E V A P O R A T O R PRESSURE
E V A P O R A T O R PRESSURE
C O M P R E S S O R N O R M A L
D IS C H A R G E PRESSURE
If cooling remains low after
pressure is normal, check
the
discharge pressure.
Check installation of capillary
bulb. If bulb is secured properly
and pressure is high, remove
bulb from pipe. See Note ”D . ”
Check for proper seal around
evaporator core and temper­
ature door.
E V A P O R A T O R PRESSURE
R E M A IN S T H E S A M E
E V A P O R A T O R PRESSU RE
IN C R E A S ES
Valve is stuck open and too much refrig­
erant is entering evaporator. Replace
expansion valve. See Note " E . ”
Check for clutch slippage,
belt slippage and listen
for unusual noises.
CHEVROLET SERIES 70-80 H EAVY DUTY TRUCK SH O P M A N U AL