Huge amp drop on G3X

[sea2jet]

There might have been a Red X briefly that I might have missed. Each time I looked at it, a negative number was displayed.
quite a few aircraft in the pattern at the time kept me looking outside.

[Andy]

Unrelated to the current issue but I notice that your log does not start until after engine start and stops before engine has completely shut down. That means you are not recording data that may be useful in some future investigation.

Quite a long time ago I ran some tests in the hangar and was upset when I got home to find I had no data recorded. I asked Garmin for the conditions that had to exist for the data log to run. I was told:

The data log begins when at least one of the below criteria are met:
Have a valid GPS fix
Engine running
System is in the air
Autopilot is engaged

I power IBBS, and usually have a GPs fix, before engine start and only power off IBBS after I have logged times after engine stop. I'm curious to know your power up, start, stop, power down sequence.

[sea2jet]

I’ll follow that procedure in the future. That is good information to know. Thanks Andy. I’ll update the thread once I remove the G3X to access the shunt and see what the issue might be.

[Pete D]

I ordered a couple of blade fuse holders and 1 amp fuses in case there are glass fuses installed. I read over on the RV forum that others have had the same erratic readings with swings into the -600-700 amp range when using glass fuses and after changing out to blade type fuses, the issue went away.

If the builder used CC provided wire harness the inline fuses would be blade type, not glass.

[sea2jet]

This is what was installed. Large enough to power a power amp in a low rider, LOL. I changed over to 1 amp blade fuses and plan to run it either tomorrow or Wednesday. Interestingly, the 1 amp glass fuses were longer than the 30mm you usually see and it was hard to remove them because the coil springs inside were coil bound. Maybe that had something to do with it, or at the connection going from a 24 gauge wire or smaller to a 12 gauge wire in the fuse holder.

[Pete D]

This is what was installed. Large enough to power a power amp in a low rider, LOL. I changed over to 1 amp blade fuses and plan to run it either tomorrow or Wednesday. Interestingly, the 1 amp glass fuses were longer than the 30mm you usually see and it was hard to remove them because the coil springs inside were coil bound. Maybe that had something to do with it, or at the connection going from a 24 gauge wire or smaller to a 12 gauge wire in the fuse holder.

Interesting, those were not supplied by CubCrafters. This may have been a custom built panel in the field for the kit.

Review the Garmin install guide on this, there are separate attach points for the heavy load wires and the small sense wires. We have seen installations where someone attaches the sense wires to the same place as the load wires and that can cause issues as well.

See the green circles (there should also be boots on at least the large wire attachment studs)

Shunt example.jpg

[Andy]

The fuses and the poorly protected terminals all go away if a Hall effect sensor is used. I used an Amploc KEY100 sensor when I added alternator current monitoring to my FX-3. I expect to replace the battery current shunt with a KEY100 at some time.

[sea2jet]

Thanks Pete, fortunately, everything was connected properly and I do have boots protecting the terminals. I was able to fly the airplane today and it worked perfectly after installing the 1 amp blade type fuses. Hopefully that fixed it. I appreciate the help.