Erratic EGT

[dahugo]

My number 3 has gone nuts. Negative values, then reading right, then the next second 800 degrees below the rest. There is no problem with the engine I am quite sure, so it must be a wiring issue.

I have 120 Hours on the plane and this just started. Per one of the threads here, I pulled the Dynon 180 and unplugged the appropriate plug to recrimp the connection, but it is a factory plug and I don't think I can just "pull" a wire and recrimp it. Even if I could, the 180 install manual does now show which pin is the #3 EGT.

The cowl is off and I am doing my annual, so I double checked all wires going to #3 and they all look OK.

Any ideas?

 

[mmarien]

I think an erratic EGT reading is a sign the probe is fried. I fried all of mine - see below. I replaced them this spring with a little more expensive ones ($90ea) and they all work fine now. EGT probes seem to be a consumable. That is they don't last forever.

 

[JohnWF]

RV-12
Rotax 912ULS. EGT left reading is solid around 1185. Right one reads in that range also, but keeps jumping up and down, usually around 20-degrees; sometimes a lot more...always the same. Connections checked....may disregard this, but would like to solve the 'why' question.

 

[Dynon]

Has it always done this, or is it new after some amount of hours?

 

[JohnWF]

Jumping EGT on one side of the 912uls began after about 125-hours on the engine. Sometime, not always, the jumping egt will start out maxed out, then return to the proper range and jump around after engine startup. the jumps are centered on about the same reading as the other side which only moves up or down a degree or two in flight and even that is at a very slow variation. Due to a LOT of wires all bunched up I am reluctant to swap sensors unless I really have to because of the amount of work involved. The system is useable as is so there is no extreme need to fix it, but I would like to know why its doing the jumping.

 

[Dynon]

Our guess would be either a probe that's on its way to failing, or maybe a wire or other connection that's become intermittent. The spade connectors on the EGTs are a reasonable place to look, if they're accessible.