I solved my erratic EGTs- bad grounding.

I added ground straps from both alternators to the engine case, a strap between the engine halves, and removed, scotch brighted and sprayed contact cleaner on all grounds. Problem solved.

I also had an intermittent heading (it would X out). The above helped, but calibrating the magnetometer again at a compass rose in a remote corner of a large airfield (Goose Bay) fixed this.

Now, I am having problems with the G900X MFD map page. It displays a "Loading" message for a very long time. (All other pages and functions appear to be working fine). It hung for so long we had to power down and restart the MFD over the North Atlantic. Not cool.

That cured the problem, but the MFD locked up again while manuvering right beside the Olympic restricted airspace in London the next day. Really not cool.

Garmin says that this is a new one. Has anyone seen this? (I have 10 software and the international Jepp database).

Regards
Clark
Legacy, 130hrs tt

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I have a Garmin G900X in my Legacy. I have erratic EGT readings on all 6 (in flight)   They read around 100F low and are erratic in an about 200F range.

All other temps and reading are fine.

The problem goes away completely when I shut off both alternators. (Shutting off one does not do anything).  No other electrical items have any effect

Note-shutting the alternators off does Not have any  effect on the stormscope or radio noise (there is none) 

We replaced the GEA engine interface box. We replaced all EGT senders and completely redid all EGT wiring from probe to panel. We used thermocouple connectors. We added a second engine ground strap. We checked all grounds.

I do Not get any radio noise and reception is great. The WX500 is clear out to 75 miles.

Garmin has not been much help. Has anyone encountered this or have any suggestions?  We are at a loss.