Chrysler DODGE D150 1993 Service Manual page 1467

24 - 30 HEATING AND AIR CONDITIONING
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up, down or to either side and can be shut off by
pushing the vanes up. Floor air is delivered through
the lower outlets.
VACUUM CONTROLS AND CIRCUITS
For an explanation of the vacuum and electrical
logic t h a t controls the operation of the unit (Fig. 1
and Control Chart).
MODES—The vacuum and electrical logic is deter­
mined by the push button switch. The vacuum por­
tion of the switch controls the water valve and
positions all doors in the unit except the blend air
door. The electrical portion of the switch controls the
compressor and blower operation. The following is a
breakdown of the vacuum and electrical logic for
each mode. Refer to Control Chart in this section.
OFF
Vacuum application is as indicated in Fig. 1. The
inlet air door is closed to outside, open to recirculat­
ing air. The mode door is in the A/C position. The
Heat/Defrost door is in the Heat position. The heater
core coolant flow is shut-off.
No air flows through the unit and the compressor
is idle because the blower and compressor clutch cir­
cuits are open.
MAX A/C
All of the doors are in the same position as they
are in Off. The Max. A/C mode merely closes the
electrical circuits to the blower motor and the com­
pressor clutch. This mode is recommended for initial
cool down, extreme outside humidity or high ambient
temperature.
A/C
This mode is recommended for use after the vehicle
has been cooled to the desired temperature. The vac­
u u m application at the outside-recirculating air door
actuator is transferred to the rod side. This moves
the door away from the outside-air inlet and closes
the recirculating inlet. The water valve is open. All
other vacuum applications and door positions are the
same for the Max. A/C position. The blower motor
and compressor are on.
VENT
The vacuum circuit remains the same as in the
A/C position but the compressor clutch electrical cir­
cuit is opened, preventing the compressor from oper­
ating. The blower motor is used to force outside air
into the passenger compartment through the A/C
outlets in the instrument panel.
HEAT
In the Heat mode the outside air door is open same
as A/C mode.
Vacuum is applied to the top side of the air condi­
tioning door actuator. This will close off the passage
to the air conditioning distribution duct and open the
passage to the heater/defroster duct. Since the heat­
er-defroster door is in the heat position, the full flow
of heated air goes through the heater outlets. A
small amount of heated air will bleed through the
defroster outlets. The water valve is open, the blower
switch is activated and the compressor is off.
DEFROST
When the defrost mode is selected all conditions
are the same as for heater operation, except t h a t no
vacuum is applied to the defrost door actuator. The
defrost door is spring loaded to the defrost position.
The door opens the defroster outlets and partially
closes off the heater outlets. The heater outlets are
left open far enough to direct about 30 percent of the
air to the floor. The other 70% is defrost air directed
to the windshield area. The compressor clutch will be
engaged.
ELECTRICAL CONTROLS AND CIRCUITS
The electrical feed for the air conditioning circuit is
from 2 fuses in the fuse block. A 20 ampere fuse pro­
tects the compressor clutch circuit, and a 30 ampere
fuse protects the blower motor control circuit.
CONTROL TEST
Test operation of controls in the following manner.
(1) Inspect compressor drive belt. Adjust, if neces­
sary.
(2) Start engine.
(3) Move temperature lever to extreme left (cool)
position.
(4) Push A/C button.
(5) Refer to Control Chart. Check position of doors,
operation of compressor clutch, blower motor and wa­
ter valve. The water valve is open when there is no
vacuum to valve.
(6) Check blower switch by moving it to all 4 posi­
tions and noting air flow change. In case of malfunc­
tion refer to Electrical Control Circuit.
(7) Check operation of blend air door by moving
temperature lever from full warm toward cool posi­
tion. Discharge air temperature should change with
lever movement if the engine coolant is warm.
(8) Repeat steps 5 and 6 in each push-button posi­
tion.
If actuation of the doors is slow or incomplete,
check for mechanical misalignment, binding or vac­
u u m leaks. The air conditioning door has a seven
second vacuum delay in mode switching from Off,
Max A/C, A/C, or Vent to Heat or Defrost. Check
temperature control cable for correct adjustment.