6.1. Testing One-Way Valves
6.1.1. Many vacuum operated circuits use in-line one-way valves to apply vacuum in one direction only.
6.1.2. to test the function of the valve remove it from the circuit. Attach the Vs4021 vacuum tester (fig.7) and operate pump to apply vacuum. In one direction the
valve should hold vacuum and in the opposite direction it should not.
6.2. Testing electrically Operated Vacuum solenoids
6.2.1. 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 Vs4021 is extremely simple.
6.2.2. locate the solenoid to be tested and remove the line that goes to the component being tested. connect the Vs4021 to the solenoid port (fig.8) 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 and breaks.
6.3. Testing Thermal Vacuum switches
6.3.1. 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.
6.3.2. 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 Vs4021 vacuum tester to the port (fig.9) 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
noted.
6.4. Testing Vacuum Operated Heater Taps
6.4.1. 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'.
6.4.2. to test these remove the supply line from the tap vacuum module and connect the Vs4021 vacuum tester (fig.10). 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.
6.5. Testing Vacuum Operated Remote central locking systems
6.5.1. 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.
6.5.2. In either system, the Vs4021 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 Vs4021 vacuum tester (fig.11) 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 Vs4021 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.
6.6. Testing Automatic Transmission Vacuum Operated Modulator Valves
6.6.1. 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.
6.6.2. the Vs4021 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
Vs4021 vacuum tester. operate the vacuum pump until approximately 15inHg is achieved and monitor the gauge reading for approximately 30 seconds.
no vacuum drop should be noted.
6.6.3. 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 Vs4021 vacuum tester (fig.12). start and run the engine and apply vacuum pressures. Monitor readings and confirm that these
are in conformance with manufacturer specifications.
6. ADDITIONAl VAcuuM sysTeMs
Original Language Version
© Jack sealey limited
fig.7
fig.8
fig.9
Vs4021 Issue: 1 - 08/06/12
