AIR BRAKES - GENERAL INFORMATIONdata includes the owner’s name, model, serial number,and GVWR for both the tractor and trailer. All of thisinformation (except the owner’s name) can be obtainedfrom the certification labels.PRESSURE BALANCE AND PRESSUREBUILD-UP RATE (TIMING) TESTConditions: This test is performed on the combinationvehicle (tractor-trailer) with wheels blocked, parkingbrake released and air system fully charged.1.Connect two test hoses to a duplex gauge.2.Connect the hoses from the duplex gauge to thecombination vehicle (Figure 26) as follows:a.One hose to the left service brake chamberon the tractor’s rearmost axle. The gaugereadingfrom this connection will be used as areference for comparing pressure andtiming differences with other axles.b.The remaining hose to the left servicechamber on the traller’s rearmost axle.NOTE-- If unused chamber ports do not exist, It will benecessary to disconnect the service brake hose, Install atee fitting between the service brake hose and chamber(Figure 27), and then connect the test hose to theremaining opening In the tee fitting. 3. Check pressurebalance as follows: While observing the duplex gauge,slowly apply the service brakes in increments of 34 kPafrom 34 to 207 kPa (5 psi from 5 to 30 psi) andincrements of 138 kPa from 207 to 621 kPa (20 psi from30 to 90 psi)Figure 26 - Test Connectlon8 - Single TrailerCTS-4154Y - Page 29
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