- Block the wheels.
- Install accurate test gauges into the front and rear dual application
valve circuits.
- Start the engine.
- Charge the air system to the air compressor governor cut-out point.
- Stop the engine.
- Depress the brake pedal to several positions between fully released
and fully applied.
- Check the delivered air pressure on the
test gauges in order to see that it varies equally and proportionality with
the movement of the brake pedal.
After a full brake application is released, the reading on the test
gauges should fall off to zero promptly. The rear brake circuit delivery air
pressure will be about 14 kPa (2 psi) greater than the front
brake delivery air pressure with both service air reservoirs at the same
pressure. This is normal for this valve.
- If the dual application valve does not operate as described, overhaul
or replace the dual application valve. Refer to
Air Brake Application Valve Replacement
or
Air Brake System Description and Operation
.
- Drain the air reservoirs.
- Remove the test gauges.
- Start the engine.
- Charge the air system to the air compressor governor cut-out point.
- Stop the engine.
- Check for proper brake operation.
- Remove the wheel blocks.