Garmin G3X and GEA 24 temperature indication issues

Hello everyone,

It's been 8 weeks since my aircraft was delivered with new Garmin glass panel including G3x Touch with GEA 24, G5 for back-up, GMA345, GTN650xi, GTR 20, GTX 345 and GFC 500.

Ever since day 1 some indications have been erroneous all the time. First of all, manifold pressure indicates about 2 inches below the actual local ambient pressure with the aircraft engine off. Oil temperature fluctuates anywhere between 97º and 135º during warm-up and throughout the flight. Never goes any higher than that and you can imagine what goes through my head when flying at 6,500 feet, 65ºf OAT and the oil temperature is at 120º. CHT for the warmest engine (#1) tops at about 340º and the coolest one (#6) at the same time is 190º. the rest just go from high to low in between like a stair. That is more that 150º difference. The EGTs are not as crazy different, maybe 30º or 40º between the hottest and coolest.

My main concern is the CHTs and the oil temperature. I have done all sorts of troubleshooting including changing thermocouples and sensors with new ones, Garmin sent a new GEA 24, wiring has been checked over and over, programming and configuring on the G3X as well Garmin is still looking for a solution but in the meantime it's been 8 weeks and I'm still grounded with no answers.

Anyone here has had an experience like this? Any new ideas/suggestions?

BTW, my plane is a 1980 Cessna C182Q with an O-470-U engine. Before the avionics exchange, it used to run a bit on the hotter side since it has all-6 new Millennium cylinders since 50hrs ago.

Thank you!


  • planewrenchplanewrench IA 48yr A&P DAL A/C Inspector

    While your wiring may be fine, double check where your ground for the unit is. On my JPI, they are adamant that the ground for the unit is at the engine CASE. not a airframe ground. Check ground path from eng to the airframe too. Eng to mount, mount to airframe. Loose or poor pin on the plug may cause issues too. I am leaning to the ground because you have too many issues, ground is common to all. CArl

    IA 47yr A&P DAL A/C Inspector 172n

  • Thanks for your input Carl.

  • edited December 2023

    If it isn’t grounding It sounds to me like it is a software display issue. I am not familiar with the units but can they be firmware updated in some way. Is there a calibration setting your shop can perform and get at least a baseline reading. It seems too random to be a probe/thermacouple issue. Maybe check the connections on the leads to the harness? I have an insight G4 and sometimes the probe leads come unscrewed from the wire harness at the connection. Or maybe it’s a wire isolation issue are they routed anywhere near any plug / magneto wires? I would try to separate them from any obvious sources of high power and or RF.

    my oil temp on my 0470U reads really low too. I rarely see over 120. I actually replaced my vernatherm thinking it was the issue. No change at all in oil temps.

    I think it is the probe in the front of the engine is getting cooled by blast air coming in the cowling.mine is on the recommended front left position. We covered the front of the probe with a bit of firesleeve and it raised it a bit. Not much. I posted about this issue here somewhere. I was originally worried about it until i talked to a Continental rep at OSH he said if your CHT’s are high enough and you’re not having issues don’t worry. I just like to see it raise before I fly then i kinda forget about it. I also have a factory oil temp gauge in the plane and it is always in the green so i don’t worry too much.

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