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4322 BaroCheck Failures

The BaroCheck is used to correct for zero drift on the A150K pressure module.  BaroCheck is required every 30 days and if it's not performed after 35 days then it locks out access to the 4322 menus.  The three main reasons why it might fail:

  1. Thermal Instability.  The temperature needs to be stable to ≤ 2°C per cycle.
    • make sure the main fan is operating.  (it will be the loud, obvious fan sound).  If not, remove the controller chassis from the metal case, trace the fan power wires and make sure the connector harness by the pump motor is firmly seated.
    • The BaroCheck routine will stop after four cycles if temperature stability can't be attained.


  1.  Leaks!  The System pressure stability must be ≤ 0.01%Rdg per second.
    • test at near 300 psi.  This is the upper range for the internal pump.  It's easier to detect leaks at higher pressure.
    • ≤ 0.03 psi /sec = PASS
    • Some of the BaroCheck failures can be corrected by paying attention to the CPS unit.  NAVAIR has found where cleaning the o-ring seals on the bottom of the CPS eliminated a BaroCheck failure, as did cleaning the filters on the CPS eliminated another BaroCheck failures.


  1. Excessive slope change.  Commonly associated with long term storage of the 4322 – many of the systems being fielded from the warehouse have (or will) experienced this.  The corrective action is:
    • Run an Alignment routine on the A150K sensor module.  Compare and adjust to the King 3689.
    • See sections Page 7-9 Operators manual; p.3-8 Service manual
    • Finish by running BaroCheck
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