A320 flight crew reported a TCAS malfunction during an airborne conflict situation.

Attributes
ACN	1607740
Time
Date	201901
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Aircraft 2
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Traffic Collision Avoidance System (TCAS)
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 167 Flight Crew Total 3348 Flight Crew Type 647
Person 2
Function	Pilot Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 166 Flight Crew Type 459
Events
Anomaly	Aircraft Equipment Problem Less Severe Conflict Airborne Conflict Deviation - Altitude Excursion From Assigned Altitude

Narrative:

The aircraft was in cruise at FL360 in clear conditions. I noticed a message on the nd (navigation display) that said 'decrease range TCAS.' when I decreased the range on the nd the TCAS showed a TA in yellow. The aircraft was at our altitude climbing very slowly. The target changed to a descend RA. The first officer (first officer) and I followed SOP and complied with the RA. I notified center that we were deviating from our clearance due to an RA. We descended about 200 feet when I visually acquired the aircraft flying over us. At this point the target was 1000 feet above us according to the TCAS display. When we were clear of conflict; we climbed back to our previously assigned clearance and notified ATC. There were no aural warnings at all from the TCAS system. When we arrived [at our destination]; we wrote up the TCAS. Maintenance repaired the system and it tested good with the 'TCAS system test ok' aural message.

Original NASA ASRS Text

Title: A320 flight crew reported a TCAS malfunction during an airborne conflict situation.

Narrative: The aircraft was in cruise at FL360 in clear conditions. I noticed a message on the ND (Navigation Display) that said 'decrease range TCAS.' When I decreased the range on the ND the TCAS showed a TA in yellow. The aircraft was at our altitude climbing very slowly. The target changed to a descend RA. The FO (First Officer) and I followed SOP and complied with the RA. I notified Center that we were deviating from our clearance due to an RA. We descended about 200 feet when I visually acquired the aircraft flying over us. At this point the target was 1000 feet above us according to the TCAS display. When we were clear of conflict; we climbed back to our previously assigned clearance and notified ATC. There were no aural warnings at all from the TCAS system. When we arrived [at our destination]; we wrote up the TCAS. Maintenance repaired the system and it tested good with the 'TCAS system test OK' aural message.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.