Chrysler DODGE D150 1993 Service Manual page 1450

• HEATING AND AIR CONDITIONING 24 - 13
Start Vacuum Pump Tool C-4289 and connect the
Vacuum Test Set Tool C-3707. With the
prod
blocked, adjust bleed valve to obtain a vacuum read­
ing of exactly -27 k P a g (8 inches of mercury) - (Fig.
7).
VACUUM PUMP
Fig. 7 Adjust Vacuum Test Bleed Valve
It is essential that the bleed valve be adjusted so
the vacuum gauge pointer will r e t u r n to exactly -27
kPag (8 inches) with the prod blocked. Otherwise a
false reading will be obtained when the control cir­
cuit is tested.
Alternately release and block the hose prod several
times. Make sure the bleed valve is adjusted so the
vacuum gauge pointer returns to exactly -27 kPag (8
inches of vacuum) when the prod blocked (Fig. 7).
Disconnect engine vacuum source hose at engine
intake manifold and insert vacuum tester hose prod
into source hose leading to push button switch. Place
vacuum gauge on the cowl so it can be observed from
the driver's position as push buttons are operated.
Start the test by depressing the control HEAT
mode button. Vacuum tester gauge needle will drop
until the actuator has operated. It should then return
to -25 to -27 kPag (7-1/4 to 8 inches) depending on
vacuum leakage. Continue to depress; OFF, MAX.
A/C, A/C, V E N T , D E F R O S T and H E A T mode but­
tons. Allowing time for actuators to operate after
each button is pushed and for the vacuum to stabi­
lize. Note the vacuum drop below -27 kPag (8 inches)
after each operation. The maximum allowable vac­
uum drop below -27 kPag (8 inches) after each oper­
ation is -3 kPag (3/4 inch). (Bypass the vacuum
storage tank if so equipped).
If the vacuum drop is more t h a n -3 kPag (3/4 inch),
first recheck the tester for reading exactly -27 kPag
(8 inches). If correct, inspect the fit of the 7 port hose
connector plug on the push button switch. This plug
must be positioned all the way onto the 7 ports on
the push button switch.
C A U T I O N : D o not use lubricant on the switch ports
or in the holes in the plug, a s lubricant will damage
the vacuum valve in the switch. If it is difficult to
properly position connector plug on the switch
ports, put a drop or two of clean water in the con­
nector plug holes. This will allow the plug to slide
completely on the switch ports.
If vacuum drop is now within limits, proceed with
the over-all performance test. If vacuum drop is still
in excess of -3 kPag (3/4 inch), remove 7 port connec­
tor from switch and seal port No. 6 with a finger to
check source hose. Then remove prod from source
line and insert it alternately into each connector port
except No. 6 (Fig. 8).
Fig. 8 Vacuum Tube Assembly Test
Note amount of vacuum drop below -27 kPag (8
inches) after each actuator has operated. If vacuum
test gauge comes back to -27 kPag (8 inches) at each
of the 7 ports, the hoses and actuators are not leak­
ing. The control switch is faulty and must be re­
placed. If excessive vacuum drop shows up at one or
more ports in connector block, isolate faulty hose or
actuator.
Inspect hose connections to the actuator involved.
Then test whether actuator or hose is at fault; use
the test hose on the actuator involved (Fig. 9).
A leak in a hose may be detected with vacuum test
set by running the fingers along the hose and watch­
ing vacuum gauge reading. The tube can be repaired
by cutting out the "leak" and inserting the tube ends
into a 3 mm (1/8 inch) inside diameter rubber tube.
Wet the tube with water to aid assembly.
A vacuum drop in excess of 3 kPag (3/4 inch) below
-27 k P a g (8 inches) will not interfere with engine op­
eration. A rough idle may occur. It can, however, in-