Air conditioning pressure regulating shutoff valve

Effectivity: Challenger 604, 605 and 650 aircraft  

ATA: 21

By: Costantino Raspa — Technical Services

Is your aircraft experiencing insufficient cooling or heating? Is there a reduction in air flow into the cabin or cockpit? Does the air conditioning unit not shut down or turn on upon command? 

If any of these conditions occur, the Pressure Regulating Shutoff Valve (PRSOV) P/N 604-97602-1 (VPN 3213876-12) could be one of the reasons the air conditioning is malfunctioning.  

There is one remedy to this problem that should be considered.   

Before you replace the valve, try cleaning the internal filter first (illustrated in yellow in the image above). With the passage of time, the filter can become contaminated with ground air pollutants, or worse, oil contamination. 

Cleaning is an economical approach and should be your first attempt to resolve any of the symptoms described above. The cleaning procedure resides in TASK 21-51-34-130-801 of the applicable Aircraft Maintenance Manual. If the cleaning materials and/or equipment are not readily available, it may be more practical to replace the filter with a new one. Filter P/N 3179746-1 can be purchased directly from Honeywell or Bombardier Spares. The part number of the filter can be found in the applicable Component Maintenance Manual CMM 36-14-61. 

Information on cleaning or replacing the filter can also be found in the troubleshooting module of SmartFix Plus under ATA 21-00 (Air Conditioning). Select “By Observed Faults” then select “215OBS001 – Low Flow in Cabin or Flight Deck.”