I've just installed two MGL type-K EGT sensors on cylinders 2 & 4 of my Rotax 914UL. The airplane is a SeaRey (high-mounted pusher prop), so there is a significantly long run (18 feet) of k-type thermocouple wire between the sensor and the back of my AF-5500. I used overlap-type (solderless barrel) connectors to splice from the sensor to the extension wire, then crimped D-Sub pins on the thermocouple wire for the EGT sensor 25-pin connector. When I fired up the engine, both EGTs were off-the-scale high within 20-30 seconds at idle throttle. For fun, I reconnected the sensors using 22-AWG wire for the long run from the sensor to the EFIS - same result.

Do I need to account for the long length of wire somehow? The AD_VALUEs were identical (I believe > 4000, but did not note it before leaving the hangar), leading me to believe that I was somehow maxing out the resistance sensor.

Any advice on how to troubleshoot?