CHT/EGT spikes when PTT is pushed

[Patrick J Wenzel]

Our avionics setup has a gremlin which I'm trying to chase. Pushing either PTT the CHT/EGT indications spike by about 30-60*C, regardless if the engine is running. I've untied all the wire bundles and started inspecting for random grounds and wire breakages, of which I have found a few already.

This is the setup:

SV Classic
SV EMS module
Dynon CHT/EGT thermocouples
PMA4000 com
Garmin SL40 radio

What would be the best way to approach this?

Cheers,

Pat.

edited for spelling

 

[GalinHdz]

Contact DYNON support for this issue. I had the exact same issue and they had to do a factory update to the EMS module. It has been working perfect since then.

 

[RVDan]

What GalinHDZ said. This is an radio frequency interference problem. Shield and signal grounds can also create this problem. From a wire routing standpoint, make sure the CHT and EGT wires are separated from the com antenna cables by as much distance as possible, preferably 3” or more.

 

[swatson999]

Known problem. You'll have to send the EMS back to Dynon, but they know what the issue is and how to fix it. Had the same thing on mine when first installed.

 

[Patrick J Wenzel]

Thank you all, will do!