We had an A&P wired a GDL 39D to our G3X few months ago. All G3X displays seemed fine initially but we noticed some fluctuations in the EGT/CHT temperature readouts with all the indicators went up and down at the same time.
Few weeks ago, the problem got worse with the EGT/CHT temperatures dropped way down to the abnormally low range (100's for CHTs and 500's for EGTs).
My initial thought was that some of the wires or plugs were disrupted when the A&P added new wires. I removed the J732 plug to check all the pins, continuity etc and could not find any broken wires or pins.
Since all the temperature readings move up and down together, I suspect the problem might be due a faulty reference temperature. The G3X P732 connector diagram shows pin 9 for Thermocouple Ref In Lo and 10 for Thermocouple Ref In Hi. However, there were no pins inserted to these positions (ie no thermocouple wires!).
The only thing I could was that the screws to hold the ground wires to the Jackscrew backshell seemed to be not very tight. I tightened the screws then made sure the J732 plug was in tight. This 'fix' seemed to work initially with all the EGT/CHT temperatures back to the normal range for the first flight. The problem came back in the second flight with the fluctuations started shortly after the flight and got worse with time.
I repeated the process one more time and found the same pattern. The 'fix' only lasted for one flight. The fact that all the readings were normal on the ground but fluctuated then dropped to the mud as the flight progress seemed to indicate something was loose and got worse with vibration (and may be heat?).
This is quite puzzling. I'd appreciate all suggestions on how to figure out the problem and/or where to find an avionic shop in NY/CT area. The avionic shop on the field in KPOU does not work on experimental stuffs. The A&P who wired our GDL39D is a very nice guy but he does not seem to be very experience with the G3X (I helped him a bit with the diagram and wiring suggestions based on what I learned from this forum).
Thank you in advance for your comments/suggestions.
Few weeks ago, the problem got worse with the EGT/CHT temperatures dropped way down to the abnormally low range (100's for CHTs and 500's for EGTs).
My initial thought was that some of the wires or plugs were disrupted when the A&P added new wires. I removed the J732 plug to check all the pins, continuity etc and could not find any broken wires or pins.
Since all the temperature readings move up and down together, I suspect the problem might be due a faulty reference temperature. The G3X P732 connector diagram shows pin 9 for Thermocouple Ref In Lo and 10 for Thermocouple Ref In Hi. However, there were no pins inserted to these positions (ie no thermocouple wires!).
The only thing I could was that the screws to hold the ground wires to the Jackscrew backshell seemed to be not very tight. I tightened the screws then made sure the J732 plug was in tight. This 'fix' seemed to work initially with all the EGT/CHT temperatures back to the normal range for the first flight. The problem came back in the second flight with the fluctuations started shortly after the flight and got worse with time.
I repeated the process one more time and found the same pattern. The 'fix' only lasted for one flight. The fact that all the readings were normal on the ground but fluctuated then dropped to the mud as the flight progress seemed to indicate something was loose and got worse with vibration (and may be heat?).
This is quite puzzling. I'd appreciate all suggestions on how to figure out the problem and/or where to find an avionic shop in NY/CT area. The avionic shop on the field in KPOU does not work on experimental stuffs. The A&P who wired our GDL39D is a very nice guy but he does not seem to be very experience with the G3X (I helped him a bit with the diagram and wiring suggestions based on what I learned from this forum).
Thank you in advance for your comments/suggestions.