EGT jumping up and down - but only in wet weather

[tweak]

The temp reading is typically jumping up and down 100-250° after startup on a rainy day. The more moisture in the air, the more it jumps. After a while it settles back to normal.

Of course i suspect the wire, but i can't really see anything obviously wrong with it. It's always dry under the hood so the wire isn't soaked in water or anything. After some driving its slowly going back to normal.
Once I was cleaning under there and then the EGT ran completly wild and was jumping 400°

Not the biggest issue, but it would be nice to get a starting point what to look for. Perhaps i should change the wire?

[rob@vems.co.uk]

Best thing to do is short the k-type wire as close to the unit as possible, this will create a thermocouple junction which will be measuring the temperature at the join, if the values continue to jump then your wire and sensor is fine.

[tweak]

I talked to the manafacturer of this type of termocoupled sensors, and it turns out that the mantel which containing the termocoupling (the metal-sticker which feels the exhaust temp) is normally filled by aluminium oxide. In case if this mantel is not properly sealed, it will suck humidity and give a false reading. However, after a stay in hot enviroment, it quickly will get rid of the humidity and sensor back to OK.

I still have left to do the physical test described by Rob, but this looks very much like the possible problem.