Sudden loss of exhaust and cylinder head temperature indication

Remington08

I recently observed the sudden loss of temperature indication of cylinder head and exhaust on one cylinder (Cherokee 6-260) at cruise altitude with OAT just below freezing. While preparing for an immediate landing, about 3 minutes minutes alter, both temperature readings resumed normal readings. After gaining altitude over the airport and circling for about 10 minutes, the temperatures remained normal with no further anolomies.

Thoughts?

MikeJJ

It would be nearly impossible for a “sudden” loss of cylinder head temperature while cruising along as the thermal mass of the cylinder would slow any temperature change. EGT can suddenly drop but less likely CHT. You did not mention any other symptoms like rough running so my first thought would be an instrumentation problem. Perhaps an intermittent connection?

Scott Sherer

I agree, Mike. It sounds like an instrumentation issue and most likely an electrical wiring issue.

empannin

The other way to look at it is if the EGT was really zero the cylinder would be dead and the vibrations extreme.

Typically if one or the other goes out I would suspect the connections to it or rubs on the wire. If they both go out at the same time I would expect a connection to the engine monitor. These sensors are measuring small signals, are sensitive to connection quality and are generally not tied to a common ground like some sensors.

Remington08

Thanks to all that commented. Very helpful. I plan to start investigating today. Annual is scheduled for next month, so I should get confirmation very soon.