I am in the process of wiring a Garmin 496 into my 182, using the
Garmin supplied accessory data cable. After reading about all of the
problems with the 396 496 Data Cable connectors coming apart, I cut the
cable to about a foot, installed a male DB9 connector on the cable, and
the matching DB9 female in the aircraft. This way, future replacement
becomes simple.

This enables you to discard most of the pis*-poor thermoplastic
insulated wires, which are way too small in terms of current carrying
capacity, anyway. This way, all of the wiring under the panel can be
done with proper Tefzel ms aircraft wire, which should make your
inspector happy.

The power leads can be properly sized (24awg), the audio can be
shielded, the RS232 data lines can be shielded, etc. This minimizes the
ground drop along the Garmin Data cable ground wire, so you may not
have to use a "ground-loop-isolator" to get rid of the whine in the
stereo feed, as a lot of folks have had to do.

Also, in the event of a Garmin connector failure, you can make a new
interface cable at home, starting with a new cable from Garmin and a
new DB9 male, without ever having to stick your head under the panel of
the airplane! You can even carry a spare, and change it "on the fly"
(pun intended).

I'm suggesting that this be adopted as a "standard", so all of us that
use Garmin 396/496 portables in our aircraft can be "interoperable".
Here is the wiring that I'm using and proposing:

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GARMIN 396/496 DATA INTERFACE CONNECTOR WIRING
(Using Garmin 010-10513-00 Power/data cable and
hooded Male DB-9 connector) MGM Oct 24, 2006

Pin#.Color..Description
------------------------------------------
1....Blk....DC input
2....Wht...Alarm (active low)
3....Brn....Voice+ (Bitch in the box)
4....Blu....Port 1 RS232 Out
5....Vio....Port 2 RS232 Out
6....Blk....Common ground
7....Org...Voice- (Bitch in the box)
8....Yel....Port 1 RS232 In
9....Grn....Port 2 RS232 In

Please disseminate this as widely as possible.

Mike Mladejovsky
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