Strange CHT Reading

[flyingforfun2004]

For some odd reason when i power up my D100/D120 my CHT reads very high like 540 deg and counts down on its own. Its not like its open circuit as when i compare on the other side which is good if i remove the wire off the sensor it goes to approx -22 and back to approx room temp on the good one yet on the bad side which is faulty taking the wire off the sensor make no change, it just keeps counting down.

I assume its not a global setting i messed up as the other side appears fine.

Thanks
Kev

 

[dynonsupport]

Thermocouples will display randomly when disconnected, and two channels on the same EMS don't necessarily act the same. What you describe sounds a lot like a broken connection.

Easiest way to test this is to short the wires. If you do this, it should read about ambient, maybe plus a few degrees. If it doesn't, it's either a broken connection between the EMS and where you shorted the wires, or the EMS is bad. Don't think we've ever seen an EMS with only one channel bad (they share so much hardware that they would generally all go at once) but anything is possible.

 

[DBRV10]

Check all the pins in your connector.

The Harness made by Stein Air could be improved a little, especially with the pins pulling back due to stress in the exit of the back shell.

I have suffered this and JakeJ on this forum also has with several installations.

That might be where the problem is if its an open circuit..... :-?

 

[flyingforfun2004]

Hi Guys,

Firstly thanks for the support.

I checked it out with a meter and i can confirm there is continuity for port side to pin 22 and starboard side to pin 4. i also checked there are no shorts to any other pins with the sensors connected.

However i did find if i disconnect the sensors wires from the enginee and do a continuity test with the sensors off i also get continuity on pins 24 and 25 but only if the wire is not attached to the sensor. Once attached to the CHT sensor on the enginee there is no longer continuity there. Does this sound right to you?

All tests with power off as they were only continuity tests.

I should tell you that i beleive but i am not 100% certain that the CHT reading was ok before. I have done an installation of the 100/120 on my Sportcrusier but this is on a new aircraft and i didnt do the wiring installation on this. It came like this from the factory so i assume it would be right but as i havent run the eng yet i am a little uncertain.

I guess if i am stuck I could remove the D120 from my other aircraft and try it but i dont really want to do that.
Any advice appricaited, Kev

 

[flyingforfun2004]

Also you say short the wires, which ones do you mean the 2 cht sensor wires together? what you saying then switch the power on? I wont do this until you confirm exactly. Hopefully the continuity results should helpus decide where we go next with it.

Cheers
Kev

 

[flyingforfun2004]

Hello once again. OK guys stand down thanks.

I just had a thought that as it was using the GP inputs the one thing i had not checked was the set up on those. Sure enough when i looked at the semsor on the GP2 it was set for carb heat or something odd.I put it back to Rotax cht an hey presto all fine!!!

Its always something simple and stuipid (ME)!

Thanks a million
Kev