4.8 Testing vacuum Operated Heater Taps
Climate control ventilation systems are becoming very common on newer
vehicles and most of the systems use vacuum operated taps to control
the heating modes.
on the majority of makes and models, the system uses vacuum to turn
the heater tap 'on'. To test these remove the supply line from the tap
vacuum module and connect the VS403.V2 vacuum tester (fig.12). With the
engine at normal operating temperature locate and feel the heater return
hose. With the heater tap in the 'off' position, this hose should be cold.
now operate the vacuum pump to open the tap. The gauge reading must
hold. If the tap is in working order, the return hose will begin to heat. If the
hose does not begin to heat this indicates that the tap is faulty.
4.9 Testing vacuum Operated Remote central Locking
systems
Some makes and models use vacuum operated bellows mounted in each
door, to centrally lock and unlock the vehicles doors. These systems use
either manifold vacuum stored in a reservoir for use when the engine is
not running or an electrically driven vacuum pump which operates when
the doors are locked or unlocked. In either system, the VS403.V2
vacuum tester is ideal for testing each individual door bellows. To do this,
remove the door trims as required. remove the vacuum supply lines from
the bellows and attach the VS403.V2 vacuum tester (fig.13) and operate
to apply vacuum to the bellows. Wait for 30 seconds, no drop on the
gauge should be noted. If the bellows are found to be in order attach the
vacuum supply line to the VS403.V2 vacuum tester and operate system
to test for vacuum supply. If the vacuum supply does not exist or is low
trace back down the lines to the vacuum supply looking for kinks,
restrictions or cracked lines. repair as required and retest.
4.5 Testing One-Way valves
many vacuum operated circuits use in-line one-way valves to apply
vacuum in one direction only. To test the function of the valve remove it
from the circuit. Attach the VS403.V2 vacuum tester (fig.9) and operate
pump to apply vacuum. In one direction the valve should hold vacuum
and in the opposite direction it should not.
4.6 Testing electrically Operated vacuum solenoids
Electrically operated vacuum solenoids are commonly used in control
circuits for air conditioning / ventilation systems, emission control
systems, idle step-up systems etc. and testing the function of these when
using the VS403.V2 is extremely simple. Locate the solenoid to be tested
and remove the line that goes to the component being tested. Connect
the VS403.V2 to the solenoid port (fig.10) and start the engine. With the
system turned off there should be a zero gauge reading. now turn the
system to the 'on' position and a gauge reading equal to the manifold
vacuum should be observed. If no reading exists remove the vacuum
supply line and test for manifold vacuum at this point. If the vacuum does
exist this indicates that the solenoid is faulty or it is not receiving a 'switch
on' voltage (use a multimeter to test this). If no vacuum exists trace the
supply line back to the vacuum source checking for kinks or breaks.
4.7 Testing Thermal vacuum switches
There are many vacuum controlled circuits that must only operate when
the engine reaches normal operating temperature. This is done using
thermal switches that remain in an 'off’ position until a given temperature
is reached. To test this type of switch, remove the vacuum supply line
coming from the manifold to the switch and test for manifold vacuum. If
this vacuum is correct refit the supply line to the thermal switch and
remove the opposing line from the switch. Attach the VS403.V2 vacuum
tester to the port (fig.11) and start the engine. With a cold engine no
reading should be noted. When the engine reaches normal operating
temperature a manifold vacuum reading should be seen.
fig.9
fig.10
fig.11
fig.12
fig.13
VS403.V2 Issue: 1 - 09/01/12
Original Language Version
4.10 Testing Automatic Transmission vacuum Operated
Modulator valves
Automatic transmissions are normally equipped with a vacuum operated
modulator valve in order for the automatic transmission to detect engine
loads and adjust shift points to suit. The VS403.V2 vacuum tester can be
used to test both that the modulation valve diaphragm is serviceable and
also to simulate varying engine loads so modulator pressure readings can
be recorded. To test the modulator valve diaphragm remove the vacuum
supply line from the valve and attach the VS403.V2 vacuum tester. operate
the vacuum pump until approximately 15 inHg is achieved and monitor
the gauge reading for approximately 30 seconds. no vacuum drop should
be noted. To check modulator pressure readings attach a pressure gauge
to the appropriate port on the transmission. remove the vacuum supply
line from the modulator and attach the VS403.V2 vacuum tester (fig.14).
Start and run the engine and apply vacuum pressures. monitor readings
and confirm that these are in conformance with manufacturer specifications.
