EGT 1 crazy indication

[edemalleray]

On my lyco IO 360, the EGT 1 is reading a way too high temperature (around 1900°F when running). I have checked the sensor (which has already been replaced under warranty) by swapping with the 3. It is not the sensor . The harness is the Dynon's one.
Another detail, when still cold, if I press the PTT, the EGT 1 indication shows around 1500° (from memory)
Note that EGT 2 to 4 are working very well.
Any idea of what it could be ? :-[

 

[PhantomPholly]

They say it's a bad connection.  I have the same issue sometimes.  It always goes away once the motor starts warming.  I've crimped (lightly) the D-Sub female connectors and re-checked each and every other wire - all test for zero resistance / good continuity.

Some day the sensor will go bad and I'll replace it.  Then perhaps the issue will go away.  But, since I really don't care about EGT when the engine is at ambient and it seems to work dandy in flight, I have surrendered to the small aggravation.

 

[DBRV10]

I'll bet its a pin in the connector at the harnes side of the connection.

If you can very carefully remove the plug from the back of the EMS and look at all the pins you will find that they are staggered.

We had an intermittent EGT2 and I was discussing this with JakeJ who is down in Adelaide, he has found the same problem.

The pin pulls back out of the connector body a bit and fails to make conatct properly.

I removed the heat shrink and pushed the cables back into the connector firmly and redid the shell. Pushed everything back in by the cable cluster. No more problems.

Seems the stress applied from so many cables and the heatshrink etc pulls some pins out of the connector body .....JUST ENOUGH :'(

Thats my bet anyway.... let us know how you go!

DB

 

[jakej]

David

The 'problem' with the EGT/CHT wires is the inherent stiffness in them - I now (have done many installations) always remove the backshell and force the wires towards the dsub connector - in a way this gives some flexibility in the loom.  

To demonstrate what I'm saying is the problem, with the loom as supplied, is look at the pins while you're flexing the loom - the pins move in and out.  A small radius bend can cause some pins to retract quite markedly and can give intermittent readings 

my .02 cents worth

Jake J

 

[edemalleray]

I have done an interesting test. I have swapped EGT #1 and #3. And the reading problem is still on the 1. I have checked the line between the Dynon and the fire wall. Nothing wrong. Where is the problem coming from ?
Radio transmission disturbes the EGT #1 and only the #1. Even switching the battery off and on disturbs the reading. But only of the EGT #1

 

[PhantomPholly]

If the problem does not move with the sensor, then it is either in the cable between the connection to the sensor and the D-Sub pin, or an actual problem with the unit.

Have you removed the pin from the D-Sub and confirmed that the connection is secure, and have you tried forcing the pin further into the socket (D-Sub cover removed) while attached to the EFIS? One last thing to try is to VERY gently squeeze the female pin so that it is slightly out-of-round. It will then make for a more firm contact between the pins.

 

[edemalleray]

Thank you for the advice, I'll check as soon as the weather permits.
But I am not confident, I have another weird phenomenon at the Fuel Pressure sensor. And I don't have a clue of how the hard is designed so that I could dismiss or incriminate the hard. But good news, nothing is no go !

 

[PhantomPholly]

I don't recall which sensors are affected or whether it affects fuel pressure, but at least SOME of the sensors (the ones with a single wire) are highly susceptible to bad readings if they are not perfectly grounded. Too, if the avionics bus is not perfectly grounded to the engine you may also have issues.

Sometimes thread sealant prevents a good ground, and it may be necessary to create a ground wire for the sensor. I used a small hose clamp to make a ground strap for my oil temp sender.

Click here for picture.