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Dynon D6 and Remote Compass Problem

Brockster

Well Known Member
Dynon has been very helpful in trying to resolve this issue though a cause for my problem has not been determined. I have a D6 with remote compass installed in my left wing tip with SafeAir mount. I had been flying for several years and the heading indicator on the D6 worked fine and was accurate within a couple degrees. Since I now had access to a compass rose I decided to calibrate it. The first few calibrations the D6 gave a warning that the data was not reliable. On the 3rd try this warning had disappeared and when I finished the heading would not function correctly and not give the proper heading. I first sent just the remote compass and then both the D6 and the remote compass back to Dynon per there instruction. They could not find any problem with either unit either time. The internal compass of the D6 works but is not very accurate. The compass rose I am using is set for magnetic north and my whiskey compass verifies it is accurate. I had the proper inclination and intensity programmed into the D6 per Dynon. Dynon calibrated my system and sent it back to me. The D6 recognizes the remote compass as when I disconnect it there is a warning that remote compass not installed. Each time when I power up the EFIS with the remote compass connected the heading reads correctly for what ever direction it is facing. If I move the plane with a tow bar the heading never moves and stays on the heading it was at when powered up. If I start the engine and say taxi in left hand circles the heading indicator will move but will not read below 84 degrees or higher than 210. When making a left turn in the direction lower than 84 degrees the heading indicator begins moving in the opposite direction. I have verified that the nutplates, SafeAir stainless mount screws or the aileron counter weight are not interfering magnetically. The Sub D9 connector at the remote compass is wired correctly. I still need to verify wiring from D6 just to be sure though doubt this is the problem as the D6 recognizes the compass. I also have another EDC-10A coming from a friend just to see if that makes any difference. Looking for any other ideas as this has many stumped. All other functions of the D6 work correctly.
 
Follow up to Compass Problem

Checked continuity, resistance and for any shorts from wire to wire or wire to shield of 4 conductor cable from Dynon D6 to EDC-10A. All checked good. Voltage at EDC-10A was 16.9vdc which is correct per Dynon. Installed borrowed, brand new, EDC-10A and same problem persisted. Replaced female sub pins on both ends of cable which didn't help. Removed cable from wing root to wing tip and reconnected EDC-10A and problem continued. Removed entire cable and inspected for any signs of problems and none found. Used Belden Data cable to make up test harness from D6 to EDC-10A. Heading indicator worked perfect. Something is wrong with original cable. What could be wrong with this cable to cause the above condition that I have not already checked for? I have ordered parts to fabricate new cable and will verify operation before installing in aircraft.

This wiring with the associated unit has been installed in the plane and flying since spring of 2013. The route of the cable was from behind the panel down along the side longeron, then down the side of the fuselage under the cap for the spar carry through side supports, through the spar carry thru, out through the side wall by the aileron torque tube and then through the wing. All bends were gentle and smooth with no kinks. Could too many bends be an issue except that it worked for 4 years.
 
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Need help, Remote Compass Problem

I'm hoping someone out there can read through my two previous posts and possibly provide some direction as to what is causing this. I replaced the cable and connectors using the same route from the D6 to the remote compass out on the left wing tip. I still have exactly the same problem. The heading on the D6 operates correctly when I use a test cable that is run outside the aircraft structure. I only have the problem when a cable is ran through the structure. Could anyone explain why this might be. Nothing else in the plane is on except the EI engine instruments.

Thank you.
 
With any D6 or D10A I simply delete the heading box and remove the magnetometer and related wiring. Life is much simpler without the calibration and mounting and wiring headaches.

G5 will display GPS track (in degrees magnetic) with no magnetometer, as does a GRT Mini X and so does the MGL extreme. The GRT Mini X provides mapping features as a bonus, and will also send data WITH heading to a HUD Head Up Display. All of that for less than the D6, well perhaps about the same cost with more features.

I still keep a SIRS TSO'd compass in the ship but mag track is all I really care about. Any X95 or X96 will do that for you

Good luck!
 
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shield ground?

Since the unit works with an external cable, the problem has to be with the cable in the ship. Is it possible that the outer insulation on the shielded cable has worn through somewhere and the shield is touching the metal of the airframe, causing a ground loop? You could disconnect both ends of the cable and check the resistance from the shield ground to the airframe. Maybe you've already done that...
 
IIRC some of the avionics companies only want one end of the ground sheath grounded. Double check the detailed instructions and then try grounding the external ground sheath at the EFIS end, or only at the magnetometer end and test the results both ways.
 
Thank you for the replies.

The shield was only connected at EFIS end. Shield not shorted to air frame anywhere.

I did replace the original cable with new of same type purchased from spruce.

My personal thought is now that nothing was wrong with original cable. The test cable I used outside of the air frame wasn't shielded and heading worked perfectly.

If need be how do I turn off heading indicator so it doesn't show on screen until I get this figured out?
 
I'm sure you checked it but verify all pins are in the correct position on both ends. In my old plane I had a similar problem with first Dynon setup. I tried everything and finally was testing continuity with a 20' wire from pin to pin from the Dynon end and the mag end. Turns out the premade harness had one pin that should be providing the mag a ground was to an open slot and I guess ground was seeking from the mag through the airframe through the painted mounts. I assume the grounding was poor and intermittent. Moving the pin fixed everything.
 
Thank you for the replies.

If need be how do I turn off heading indicator so it doesn't show on screen until I get this figured out?

It is in some of the set up button options- likely on the same page you can select the magnetometer calibration. Heading display On or Off
 
Are the magnetometer wires running near other wires (e.g. heated pitot) that might be inducing a magnetic field?
 
Pins are in correct location. Also no wires with any current or voltage near cable. I think I will end up having to send D6, EDC-10A and 4 conductor cable back to Dynon as they are stumped right now as well. What is interesting is the heading works with regular solid copper data wire that is unshielded and not twisted. It seems some characteristic of the Mil Spec cable is causing a problem at this point. I will post what we eventually find as cause.
 
Yes I checked for any shorts between any of the four conductors and the shield. Problem occurs with original cable purchased back in 2012 and cable I just purchased recently. Unit just doesn?t seem to want to play nice with shielded twisted cable anymore.
 
More troubleshooting

Did some more trouble shooting and I may have narrowed it down to length of wire being used. The original cable installed was 17 foot long and the replacement was 20 foot long. The solid copper test cable I used was around 12 foot long and would always work. The 20 foot long cable creates the same problem either installed or out of the plane. The original 17 foot long cable would not work in the plane and never tested it full length out of the plane. When I originally took out the 17 foot long cable I cut it in a few spots to leave portions in the plane for ease of pulling a new cable. Wish now I hadn't done that but I was left with a 10.5 foot long piece and decided to try that. When I connected the 10.5 foot long piece the heading worked fine. So now if I connect out of the plane the 20 feet cable I can turn the problem on and if I switch to the test cable or the 10.5 feet long original cable I can turn the problem off. Now the first thought might be that the original cable had or now the replacement cable has a problem in it. I don't think so because installing a new cable 4 years later and having the same problem isn't likely. I also checked the new cable with a meter just like the original cable. Unless there is something further I can do to verify this my only option is to send back the D6, EDC-10A and the 3 cables I used and see if Dynon can repeat the problem. Thoughts?
 
Me speculating.

You are getting some kind of low level interference on the line. With the short cable, your data signal levels are high enough the unit can compensate. With the long cable, the data signal levels are lower while the interference is higher so the unit can no longer compensate.

Other than that, it has got to be an electronic gremlin.

evil_gremlin_2.png
 
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Gremlin Slayers

The EASY cure, if you are fixed on keeping the 3 1/8" round hole is a GRT MINI GA OR the Garmin G5. In both cases you can omit any magnetometer and still have a Mag trk display in the heading field.
 
The EASY cure, if you are fixed on keeping the 3 1/8" round hole is a GRT MINI GA OR the Garmin G5. In both cases you can omit any magnetometer and still have a Mag trk display in the heading field.
IMHO that is not a cure for the problem but a band-aid that only hides the symptoms. Find and fix the problem or you risk having it affect something else.

:cool:
 
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Everything should arrive at Dynon Monday morning including cables that work and don't work. Maybe my home airport has developed some type of interference, LOL. I certainly thought about just turning off the heading. Also I am not ready to drop $1100 just yet on a new instrument. This has become a quest to find out what is wrong more than needing the heading indicator. Hoping to learn something and will post when I hear something from Dynon. I did take the unit home and run it on the bench and the problem persisted with the longer cable. Stay tuned.
 
Problem resolved

Dynon found the DSAB TX RX chips were bad in the D6 and replaced them. It has been tested with the long cable and it is working as it should now. They said they will need to modify there test stand as it only has a 3 foot cable. Also they will probably change there troubleshooting protocol to help identify a problem like this. Looking forward to getting it back and reinstalled. Thank you Dynon :)
 
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