[Bill Boyd]

I'm trying to wire in a 795 into my panel to replace a 296. To economize (hey, I'm a pilot) I thought I'd sacrifice the cigar lighter charging harness as my panel mount and keep the AC docking station wiring intact for home use.

The 296 is (or rather was) flawlessly providing NMEA 4800 baud data to my Trio ProPilot through its blue TX1 out wire and common ground, and everything has been operating normally.

During the install of the 795 today, I succeeded in splicing the ship's power and ground to the heavier red and black leads in the 795 harness, and it shows it's charging from bus power when the master is on.

Here's the puzzlement. The 795/796 manual lists the wire code for the bare wire harness in Appendix D page 145. I'm looking for a blue wire for TX1 out, or an orange wire for TX2 data out. I see in my hands orange, brown, yellow and purple wires, plus a shielded sub-bundle containing smaller red and black wires as well as a twisted pair of white and green wires. I have tried all four of the orange, purple, yellow and brown wires one at a time to the data in pin on the autopilot and none allow it to pick up any NMEA data. I have set the Interface to NMEA OUT on both ports, and tried normal and fast settings (Trio says this should not matter to the A/P), and I have an active flight plan loaded and a 3D GPS position fix while trying the above. All I get is "No GPS" from the A/P control head.

I'm suspecting the pins I need are not soldered to any wires in the cable(s) I have, or that the signal I need might be on the other shielded wires (but I highly doubt that and have not tried them). Can Garmin help me out here? Is the bare wire cable you sell my only option, or can you tell me what possibly vacant pin in the docking connector I need to solder a signal wire to?

Thanks!

 

[g3xpert]

I'm trying to wire in a 795 into my panel to replace a 296. To economize (hey, I'm a pilot) I thought I'd sacrifice the cigar lighter charging harness as my panel mount and keep the AC docking station wiring intact for home use.

The 296 is (or rather was) flawlessly providing NMEA 4800 baud data to my Trio ProPilot through its blue TX1 out wire and common ground, and everything has been operating normally.

During the install of the 795 today, I succeeded in splicing the ship's power and ground to the heavier red and black leads in the 795 harness, and it shows it's charging from bus power when the master is on.

Here's the puzzlement. The 795/796 manual lists the wire code for the bare wire harness in Appendix D page 145. I'm looking for a blue wire for TX1 out, or an orange wire for TX2 data out. I see in my hands orange, brown, yellow and purple wires, plus a shielded sub-bundle containing smaller red and black wires as well as a twisted pair of white and green wires. I have tried all four of the orange, purple, yellow and brown wires one at a time to the data in pin on the autopilot and none allow it to pick up any NMEA data. I have set the Interface to NMEA OUT on both ports, and tried normal and fast settings (Trio says this should not matter to the A/P), and I have an active flight plan loaded and a 3D GPS position fix while trying the above. All I get is "No GPS" from the A/P control head.

I'm suspecting the pins I need are not soldered to any wires in the cable(s) I have, or that the signal I need might be on the other shielded wires (but I highly doubt that and have not tried them). Can Garmin help me out here? Is the bare wire cable you sell my only option, or can you tell me what possibly vacant pin in the docking connector I need to solder a signal wire to?

Thanks!

Hello Bill,

Well, you are in good company because it is pretty common for customers to contact us and tell us a similar story.

They cut up a pre-made cable and found out the hard way that these cables only contain the wires needed for their dedicated function and additionally the wires that are there do not conform to the wire colors called out in the manual for the bare wire cable/mount designed for those wanting to gain access to the serial ports, power, and audio.

Sorry, but you will want to obtain the bare wire cable. Fortunately it will be really easy to do what you want to do (and more such as interfacing to the GDL39 ADS-B receiver bare wire cable with the second serial port) since the wire colors are documented in the manual.

Thanks,
Steve

 

[Bill Boyd]

Thanks for the after-hours reply, Steve

I am not beyond unsoldering and moving a random unused wire for my custom application to the correct pin on the docking connector to access the TX1 or TX2 OUT RS-232 signal. Any way you could tell me what pins on the rear docking connector correspond to those functions?

 

[Bill Boyd]

Closure

Steve is correct; I will "want to" purchase the bare wire cable for the 795 to get nav data into my autopilot via serial connection. After disassembling the docking connector, whose cable I had ambitiously cut off in hopes of accessing the wires for RS232 data, I see that the cable interfaces to the contact pin array through a small edge connector and printed circuit board which is prohibitive to attempt any "haywire" connection to.

Lesson learned, and hopefully lesson passed along: Garmin does not use a one-size-fits-all cable in the various harnesses they provide for the 795/796. The USB/charging/audio jack cables have no unconnected wires within that can be used as a home-brew bare-wire harness substitute. If you want the bare wire functionality, you will "want to" drop another $65 or so on the purpose-made (and not supplied in the box) cable for your hookup. It probably won't be my last live-and-learn experience in experimental aviation, but at least I didn't fry or brick anything in my clumsy attempts to kludge a work-around.

I'm thankful that Garmin makes such a fine piece of avionics, and that they have dropped the price of the chart subscription for it in the wake of the 660 release. I will get over the foolish feeling I'm left with having cut up my cigarette charger/USB/audio cable - just not today