09
Testing Vacuum Operated Remote Central Locking Systems
Some makes and models of vehicles use vacuum operated bellows mounted in each door to
centrally lock and unlock the vehicle 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.
For either system, the vacuum tester is ideal for testing each individual door bellows.
1. Remove the door trims as required.
2. Remove the vacuum supply lines from the bellows.
3. Attach the vacuum tester (figure 11).
4. Operate the vacuum tester to apply vacuum to the bellows.
5. Wait 30 seconds.
6. No drop on the gauge should be noted.
7. If the bellows are in working order attach the vacuum supply line to the vacuum tester.
8. Operate the vacuum system to test for vacuum supply.
9. If the vacuum supply does not exist or is low trace back down the lines to the vacuum
supply. Look for kinks, restrictions or cracked lines. Repair any issues and test again.
Testing Automatic Transmission Vacuum Operated Modulator Valves
For the automatic transmission to detect engine loads and adjust shift points to suit,
automatic transmissions are normally equipped with a vacuum operated nodular valve.
The vacuum tester can be used to test both the modulation valve diaphragm is serviceable
and also to simulate varying engine loads so modulator pressure readings can be recorded.
Testing the Modulator Valve Diaphragm
1. Remove the vacuum supply line from the valve.
2. Attach the vacuum tester.
3. Operate the vacuum pump until approximately 15inHG is achieved.
4. Monitor the gauge for approximately 30 seconds.
5. No vacuum drop should be noted.
Checking Modulator Pressure Readings
1. Attach a pressure gauge to the appropriate port on the transmission.
2. Remove the vacuum supply line from the modulator.
3. Attach the vacuum tester (figure 12).
4. Start and run the engine.
5. Apply vacuum pressures.
6. Monitor readings and check these against the manufacturer’s specifications.
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