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Introduction
4.4 Lift Axle Operation Check
The Lift Axle Operation Check is performed after the ABS system has been properly programmed and the
Sensor Orientation Test has been successfully performed.
The trailer must have constant power applied and have air supplied to the supply/emergency (red) line.
Activate the manual override switch (if equipped) to confi rm that the lift axle lowers in an unladen state.
Once confi rmed, return the switch to its original position and the lift axle should raise.
Testing the automatic override confi guration (if equipped) that has the delivery line pressure switch in place
of the manual toggle switch requires a tractor. Correct operation should be tested after the trailer Sensor
Orientation Test has been completed. Attach the unladen trailer to a tractor and ensure both air and power
are hooked up. Release the trailer spring brakes using the red trailer brake valve on the tractor dash. The
lift axle should move to the raised position once the spring brake has released.
Apply the spring brakes (evacuating air) using the red trailer brake valve on the tractor dash. The lift axle
should lower. This completes the pressure switch test.
Add the appropriate amount of weight to the trailer so that the ride bag pressure equals or exceeds the
“Lowering Pressure” value entered into the Parameter screen. The lift axle should lower from the raised
position and the indicator lamp should extinguish.
This completes the Lift Axle Operation Check.
4.4.1 Lift Axle Test Rig
Some trailer OEMs may choose to construct an assembly to rapidly test the performance of automatic lift
axle installations using the spring brake delivery line pressure switch. Components used in the construction
of this assembly are commonly found at trailer OEM facilities. Figure 15.
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