MGL Avionics User Forum

I have an Extreme EFIS/EMS with 500 hours on a Rotax 912 uls. It uses an RDAC VD. the CHT function has stopped working. strangely enough, the unit displays the ambient temperature on both sides but will not show cht. Both cht sensors have been checked and work normally. Ground has been checked using "REF Ground" terminal. the meter shows 5 ohms between the REF/Ground terminal and the engine block gnd. K type probe is selected on setup page of EMS.
We are out of ideas. Should I send the RDAC VD unit to you guys for bench testing?

Help

OK, that sounds like you are in fact using the thermocouples as CHT senders - these will show ambient if nothing is connected.
The normal 912 CHT senders (the two that are built into the engine) do not show ambient. Those are NTC (resistive) type senders - actually they are just ordinary oil temp senders.
So it sounds like to be that you changed your EFIS setup ?