Unusual EGT reading prior to engine start

[Battson]

After 4 more flights this weekend, the problem didn't reoccur... It seems to be worse on really hot days. Maybe.   

It is still happening, even with a cold engine that's been sitting for a week... About 1030*C at the moment when it gets a false reading. Still not sure why...

Could an electrical current supplied directly onto the themocouple wire (short-circuit from an adjacent wire) create such a reading??

 

[Dynon]

Voltage injected through a thermocouple wire would definitely cause at least the one reading that's carrying the current to go nuts. Not sure about the rest of them though (will need to check with one of our engineers)

 

[Battson]

Ok - that could explain what I am seeing.
Perhaps one wire has abraded it's neighbour, as my thermocouple loom runs parallel to other power wires. I am doing a 100hr this weekend, so I will explore it.