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GRT lost GPSS steering

SVTPete83

Well Known Member
Weirdest thing. I have a garmin 650 running GPS info to my GRT Horizon EX. I have a switch so I can pic which item guides the autopolit, the efis or the gps. A few flights ago my GRT stopped giving GPSS steering commands to my trutrak vz385. If I switch it to the GPS I can get GPSS steering. But for some reason it went away when commanding it from the efis. Any ideas why this setup, which has worked perfectly for the last 10 months all of the sudden go TU? Is it possible my ARINC module went bad? I'm also afraid that once it happened I started messing with settings to get it to work and now might not have them how I had it configured. Here is a couple of screen shots of my settings. Any help you could give me would be greatly appreciated!

Original Screen shots removed-too big!
 
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90% of the time it’s wiring. Start at the gps-efis switch, trace the arinc pair back to your grt arinc, check connections. Look around for any other disconnected wires.
Your photos don’t seem to show any rs232 serial connections going to the autopilot.
 
I don’t see serial port 1 listed. Do you have an ARINC 429 installed? If so I would expect that to be identified later in your setup menu as GPS1. If you have an internal GPS that could be identified as GPS1.

You do have serial port 5 identified as GPS2 input identified as GPS2/Aviation Map/Comm. With both serial port 3 & 5 outputs defined as “Display Unit Link” you obviously have a conflict. Try configuring serial port 5 output to “Autopilot NMEA0183” and see if that doesn’t fix your problem.
 
Well randomness going on but it worked today on my flight. I adjusted nothing. Did nothing different. I’ll take a pic of all the settings so you all can check it out. I did get a random gps config warning for a moment today. But I had full autopilot controls again. All the wiring seems to be hooked up as far as I can tell.
 
Spray that efis-GPS switch with contact cleaner.

I will double check all the wiring again today and hit the switch with cleaner. When it does not work and I switch to EFIS driving the autopilot I just get Nav mode on the AP and it will still steer the plane horizontally just fine. I set up a lot of these settings myself with no prior knowledge of what I am doing. Its a dual screen horizon EX. The first set of settings are on my main efis, the second set on my other one. Let me know if you all see anything that is not right! And thanks a ton for the help! I really appreciate it!

IMG_7936 by Peter Anderson, on Flickr
IMG_7937 by Peter Anderson, on Flickr
IMG_7938 by Peter Anderson, on Flickr
IMG_7939 by Peter Anderson, on Flickr
IMG_7940 by Peter Anderson, on Flickr
IMG_7941 by Peter Anderson, on Flickr
IMG_7942 by Peter Anderson, on Flickr
IMG_7943 by Peter Anderson, on Flickr
 
I don’t see serial port 1 listed. Do you have an ARINC 429 installed? If so I would expect that to be identified later in your setup menu as GPS1. If you have an internal GPS that could be identified as GPS1.

You do have serial port 5 identified as GPS2 input identified as GPS2/Aviation Map/Comm. With both serial port 3 & 5 outputs defined as “Display Unit Link” you obviously have a conflict. Try configuring serial port 5 output to “Autopilot NMEA0183” and see if that doesn’t fix your problem.

I'll try this out as well. Thank you
 
I got it firing well today. Checked all the wiring and connections. Switch wires are soldered up and looking good. I did try the setting mentioned above with no joy. After putting serial 5 to autopilot aviation it clicked on! Hopefully it will stay that way! Thanks for all the help and advice!
 
Just in case

If this happens again you might want to look at the A/P GPSS Source DPDT switch.

I’ve been trying to upgrade my old WS system to a dual EX EFIS system and after many frustrating hours and four failed test flights discovered that switch had failed giving the exact symptoms you described. Replacing that switch is a bear because of the lack of work space and the small pins (a nine pin DPDT switch).

However I got real lucky with Aerotronics (VAF advertiser and the people who built my panel in 2006 for the original builder) and they spent hours on the phone helping me identify the problem, wired leads to a new DPDT switch, labeled each lead where it goes, and sent a wiring schematic. They just charged shipping and I got it two days later. Great company!

Another reason for having your panel built by a reputable company - follow on support for subsequent owners.
 
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