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sjjonesnz

Well Known Member
The GNS430W has two power inputs (on pins P4001/19 & 20 and P4001/15 & 72) each with their own 5A fuse/CB. The installation manual says Power Input 1 (P4001/19 & 20) provides power for all functions of the unit except COM transmitter and NAV & G/S Superflag outputs, but makes no reference to Power Input 2.

Is Power Input 2 simply a secondary/redundant feed for the unit or does it have some other purpose?

If it is just a secondary feed, why, when the manual recommends all power inputs be connected to the same bus, would I have it on a separate CB (other than the ol' redundancy thing)?
 
hummmmmm

One input is for the com and one for the nav.......both have to be connected to a buss....
 
True, however the GNS430W has a bunch of power inputs and grounds - the two power inputs I mentioned before as well as another (P4002-11/12) for COM power and a 4th (P4006-44) which is only needed if VOR/LOC and GS Superflags are used; along with two ground pins on P4001, two more on P4002 (which the manual says need to each have their own 10A CB!!!) and one on P4006.

My instinct tells me power input 2 isn't really required, nor do I need to put a CB on both of the ground pins for COM - a single CB would suffice - altho' I have been wrong before (just the once tho' ;) ). Can anyone confirm/refute my suspicions??
 
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Only hot leads (+) go to a CB. Grounds go directly to a grounding post or terminal. The power leads are small, and seem to require two leads each to carry the current.
 
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Secondary Bus

Hi,

On P4001 you only need power on pins 19 and 20 (GPS/NAV), on P5002 you need power on 11 and 12 (COM). Unless you are using the superflag output on P4006 pin 15 you don't need power on P4006 at all.

Hope this helps.
 
Garmin Wiring

Aircraft Power 1 (pins 19,20) and Aircraft Power 2 (pins 15,72) are indeed redundant connections (assuming you have only a single bus to power the 430W). Pins 19 and 20 are directly connected to each other, as are pins 15 and 72 - but the 19,20 pair and the 15,72 pair are isolated from each other by internal diodes in the 430W.

So if you have a simple electrical system, just connect Power1 and be done with it. You can feed Power 1 and Power 2 from the same source if you want to, but it won't make any difference in the operation of the unit.

If you have a more sophisticated electrical system (say two alternators, two batteries, two buses), then you can hook up Power 1 to one bus, and Power 2 to the other. In this configuration, the diode isolation assures that regardless of the type of failure that may occur one power input, the other power input will keep the 430W powered and operating.

The ground return pins (77 and 78) are common to both Aircraft Power 1 and Aircraft Power 2, and are directly connected internally.

The max current draw through these power pins on P4001 is 2.5A, so a 20 (or even 22) gauge wire is adequate. The COM section can draw up to 6A, so an 18 gauge wire with the oversize pins is the conservative choice for that connection (on P4002).

I don't know the current rating for the contacts, so the conservative approach is to hook up both pins of for each pair (19/20, 77/78, and 15/72 if you decide to use Power 2)
 
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