Amp meter Draw

[Robb]

My Rv7 always shows about 7 amps when I key the mic on my Garmin 430. I also see my manifold gauge drop a lot at the same time. It has always done this but does not seem to be a safety issue. I am going to have it looked at when i have the ads b out installed just wondering if anyone has an idea of what's up


Dues paid gladly

[GalinHdz]

1 - What kind of Ammeter? EFIS or Analog
2 - What kind of current sensor? Shunt or Hall Effect.

[rv7charlie]

The fact that an unrelated gauge is affected would indicate poor connections somewhere in the system, likely grounds, or ground path issues (ground loops).

What grounding philosophy did you use when wiring the plane?

[Robb]

Not really sure how it was grounded as I did not build it. The gauges are all analog

[erich weaver]

Originally Posted by rv7charlie

The fact that an unrelated gauge is affected would indicate poor connections somewhere in the system, likely grounds, or ground path issues (ground loops).

I don't think so. More likely he is getting radio frequency interference, with one or more wires acting as an antenna. Can be hard to chase this down. On my -7A I get a fuel pressure warning on the EFIS whenever I key the mic.

Erich

[GalinHdz]

Originally Posted by rv7charlie

The fact that an unrelated gauge is affected would indicate poor connections somewhere in the system, likely grounds, or ground path issues (ground loops).

What grounding philosophy did you use when wiring the plane?

This is the highest probability and the hardest to hunt down. Start with the radio antenna cables, connections and attachment to the fuselage. Check for broken, loose wires or corrosion somewhere. After that check all wires (especially the ground wires) starting with the affected gauges.

Good luck. These kind of gremlins are a PITA to track down.

[rvbuilder2002]

Originally Posted by GalinHdz

This is the highest probability and the hardest to hunt down. Start with the radio antenna cables, connections and attachment to the fuselage. Check for broken, loose wires or corrosion somewhere. After that check all wires (especially the ground wires) starting with the affected gauges.

Good luck. These kind of gremlins are a PITA to track down.

Another potential cause is leaky coax routed beside un or poorly shielded wire connected to an instrument.


RG400 coax is less likely to cause this than RG58.

[Robb]

Thanks Guys

[RONSIM]

If you have extra wire coiled behind the panel, get rid of it by trimming the wiring, or laying out the wires in a "non-coiled" fashion. I was getting an ammeter spike when I keyed the mike.

Ron

[jweir43]

Take a 4" square of aluminum foil, wrap it around a wire or a bundle of wires, and slide it along the wire(s) until the goosey readings stop. If you are using a bundle of wires, take them one by one and see which one kills the interference. Repeat, lather, repeat until you've checked every wire in the airplane.

At these frequencies, RG58 is every bit as good as RG400. That's the LAST resort, although a loose termination on the coax braid WILL cause the problem. The al foil will find this fault also.

Jim