Strange Carb Temp Sensor Behavior

[pnwpilot]

During the last couple of flights, the carb temp sensor reading for my HDX became erratic and oscillated up and down randomly during the flight if the temperature inside the carb went below ~45F or so. The range that the temperature reading oscillates between looks to be about minus 20F below the actual carb temperature and the actual carb temp itself. For example if the carb temp is supposed to be 40F, the HDX will show a carb temp reading that is rapidly changing between 20F to 40F over and over again. Pulling the carb heat to increase the temperature above 45F or so will stop the oscillation and show a rising carb temp. It will eventually stablize and read ok at the higher temp. The sensor was new and installed in 2018 during the CI. The sensor has performed flawlessly until the recent flights.

Anyone else experience this? All other EMS readings such as CHTs and EGTs are rock solid so I can't imagine it's a grounding issue? It's strange that the sensor would start working normally if the carb temp is higher than a certain point. Perhaps a bad solder joint inside the sensor itself?

 

[DBRV10]

Most likely a poor connection. Even if the termination looks OK, it probably is not. While there is a remote chance it is the sensor, that would be the last thing I would replace. In your hunt for faulty connections do not assume the big D Sub connector is immune so check the wire/pin is seated nicely.

 

[pnwpilot]

This was indeed caused by a bad connection except the bad connection was one of the wires going into the sensor housing. My guess is that the wire had a bit too much slack and 300 hours of inflight forces fatigued it enough to break it as the wire pulled out of the housing with ease. Replaced the sensor with new (and took out the slack a bit) and and all is well again.