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Big X thru Alternator Amps on G3X

PandaCub

Active Member
I'm wondering if there are any G3Xperts who could weigh in here before I start taking things apart:

As can be seen in the screenshot, the ALT AMPS indicator on my RV-14A's G3X has a big X thru it, as if the panel is no longer getting voltage/signal. It's worked fine until now (I did have an A&P replace the starter relay recently, but it's not clear to me how that might be related to the alternator amps indicator). The alternator appears to be charging the battery normally, as indicated by the healthy, steady voltage levels.

Could this be a software issue, where I inadvertently fat-fingered an invalid parameter into the G3X setup? Or could it be loose/disconnected shunt wires, etc? What does the X mean, anyway?

Thanks in advance for any ideas on how to get my ALT AMPS reading back!

3575-RV-14-A-ALT-AMPS.jpg


Shunt-Diagram.jpg
 
If you didn't change any settings in "menu" mode it's unlikely that a setting is the issue. More likely somewhere a wire is loose/broken or a connector is loose.

The shunt wire is the obvious place to look, and since recent work was done on a relay, could it be that shunt wire is routed in the same area? I can image how the wire might have accidentally been damaged or disconnected.

Have you tried checking all the connectors? I'd start with the easy ones i.e. back of the GDU. On my airplane the shunt wires (I think they do anyway) connect to the GEA 24, so those connectors would be a place to look also. To check wire continuity from the shunt to the GEA 24, the pins for those two wires should show a very low resistance value (almost like a short) if I understand the wiring of the shunt correctly (measure current by using a very low resistance shunt - check voltage on either side)
 
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per the G3X installation manual, the is supposed to be a fuse on each wire from the shunt as close to the shunt as possible. I would look at the area around the shunt for the fuses and all connections in that area.
 
per the G3X installation manual, the is supposed to be a fuse on each wire from the shunt as close to the shunt as possible. I would look at the area around the shunt for the fuses and all connections in that area.
Or the wire to the shunt. If I am not mistaking, the red X means that it has been configured but it is not getting signals from that configured device on the wire.
 
I would also suspect a blown fuse on the wires from the shunt to the 24. The shunt is unprotected and if your mechanic touched a wrench to it with the avionics power on, it would blow the fuse if that wrench was also touching ground.

An unrelated question. Are both of your voltage inputs connected to busses that are being fed by the alternator? I ask because my G3X gives me an accurate reading on the Volt 1 pin, but 4 to 5 tenths low on the Power 2 pin. It looks like yours is behaving similar.

Larry
 
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Could be..

Big Red X (tm) means that the G3X firmware is expecting to see a device but it is not. As others have suggested, it's probably one or both of the 1A fuses (if installed) between the GEA 24 (GEA 73) and the shunt have blown.

The Volts E level looks a lot like the measured voltage from the TCW IBBS back-up battery. In my set up it starts around 14.5V then decreases to 13.4V over about 2 hours, then the charger circuit kicks on and takes it back to 14.5V -- wash-rinse-repeat.

Cheers!
 
An unrelated question. Are both of your voltage inputs connected to busses that are being fed by the alternator?
-Larry

Hi Larry, the right "E" side of the voltmeter shows the Emergency IBBS (Integrated Battery Backup System) voltage and, as Brian describes, it settles around 13.4v after it's been charged. I'm still not sure if it's wisest to leave the IBBS switch normally on, or usually OFF and hope I'll notice the enunciator(s) if the main battery voltage gets too low.

Of course, the display shows 0v when the IBBS switch is off (and I suppose it's not charging?)

-PandaCub

ALT-AMPS-X-3205.jpg
 
The IBBS is supposed to be turned on first, left on for the duration of the flight, and turned off last.

If you don't do it this way, and you lose your main power source, the time to enable the IBBS, re-boot the G3X systems will be the longest seconds (a minute) of your life...

The IBBS is supposed to provide power seamlessly to the backed up loads without pilot intervention.

Cheers!
 
The IBBS has some unusual operating parameters though.
Without the 'pass thru' the output will turn off when charge voltage is supplied.
With the pass thru you will have voltage available at the outputs but but now you can't turn it off unless you basically turn off the master or pull the pass thru CB.

I like the ability to re-boot boxes so I generally don't wire the pass thru..

I typically wire the charge circuit of the IBBW on the avionics bus which will provide:
Back up power for starting.
Output falls to 0 with avionics bus on which allow rebooting of boxes.
(if you lose power on the avionics bus power will automatically resume from the IBBS)
 
G3X Touch Shunt Input

Good Morning,

I believe the first place to look is the wiring from the shunt to the GEA 24, including the fuses as others have mentioned.

p6dBpX9LKASD2B5aCUE5JBnu8k4IvjPos47OexjcAGnen3y2a3PtzuuC0ni5VmGCUYyww0YfznjoqEVUZ_WinsyNZmSOWsEJYvIY_vfoyK-ZQtrr4OUE8K7kuvA72Y206X87_KK_aGaM3osXDxQPZCpZySNy7WS-Y5Ho79aDP_RBJfuUvDdpsKlrj3EJ_Z5B27yOIomvM1kGYABfFYjYpeVdGICGMyQop9wqdlMdlbTKJxmV_pbRKFkjk2EMGSceoSCf8NxXghZgroWAdb3C5z3rETYkN8eQoRehMoledHGwqvVmm12V7En4kP2Dg6prBKmsQn_gjMinUd1g8HH4E7GnycumI2HT4sUWIR7CXATfGzKNFZTVEa_YlbvxEsVK3JAZkrrvBfRCFvKlPT1DoCzjjGQ7EFp5zhzn11QBtJdbsCwxlx-qpFFffL8JnObGliv0vk5-Y9U3v0hzfjHOKe5P_iEoFGkUWN5k0MkyySl90JY_txy7axrNrPx2VYEMf8BAfrEYVri6OCu6sWA0wxJNnYu7HHX0dG-FnIMH4r-_k0yK7oc0pAIfgw1sjq_LN08MPGLB0a9XG3ZEVsLOaoaSP0Gme2_V_2GZXjE-kK__JBNLYx0ux2n7EJDKfI3IQgxnuejeDmdyFvZN4kyc8M2lHp7c-igfXzXp9RNzT12er5qd=w694-h211-no


Please feel free to email us directly at [email protected] to continue troubleshooting this if no obvious issues are seen in the wiring.

Thanks,

Justin
 
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