Evening all,
I’ve created a wiring harness to install the unit in my 172. Im using a KI209A as the indicator. When bench testing the unit and following the test pages i noticed that the VOR / LOC test didnt work as I would expect. No matter what I did I could not get the crs dev needle nor the to/from flag to move. Ive now spent many hours triple checking the wiring, particularly on connector 5006, the composite in/out line. The wires are in the correct pins and there is continuity through the pins from connector to connector.
Some pictures for clarification:
The initial instrument self test panel
The CDI displaying what I would expect
The Vor / LOC test page
The indicator only displaying glideslope information and no course deviation.
The KI209A wiring diagram
Not having a VOR transmitter in my shed (yet) I cannot test it in the real world without bolting the whole stack into the aeroplane, which i dont want to do in case i have to pull it all out again. There is a posibility that this is just the behaviour of that specific test and that everything works fine.
So to cut a long story short:
does anybody know if the behaviour is correct for that test with this indicator? and thus everyting will work fine in the real world.
does anybody have any works of wisdom for other things to check?
My wiring matches the drawing perfectly and all other fucntions work fine. Ive checked the Composite and ILS engage lines many times and all seem ok.
@Georges_Shed thank you for posting am in the throes of getting a KI209A to connect to a KLN94 (am told the MD200-706 doesn’t connect), waiting on a quote for the installation and sourcing the KI209A (new they cost more than a G5 or GI275!).
Am wondering whether Garmin have antibodies to Bendix King, and vice versa.
@RobertL18C, In theory it should work fine. The garmin install manual lists many possible connections to a whole host of connectors. like most electrical stuff, it SHOULD work but somehow Doesnt. I guess this is why avionic shops earn the big bucks…
You should post the actual wires you have connected, and the voltage on each relative to ground. This is after all a simple analog (DC) system, no 400Hz sinewaves involved. The voltages will tell whether the GNS is outputting the right voltage.
Absolutely no need for “big bucks” to use one of these 
King_KI_209A_Maintenance_pdf See page 5-12 onwards, and elsewhere, for the voltages.
What is a lot harder is decoding a composite nav signal (often incorrectly called “composite video”; that is a completely different thing). I think most people do this with a KIxxx indicator they have kicking around. Any of the EHSIs e.g. SN3500 can do it also.
One person who may have an idea is @wigglyamp.
Thanks everyone for your help.
I contacted Garmin about this and they stated
“ Dear George,
Thank you for your email.
I can confirm that this is normal on the GNS units. The VOR/LOC composite signal is a signal pretty much picked off the antenna input before any internal processing within the GNS is done and sent to the indicator as a raw radio signal. The internal converter of the instrument decides, based on that raw radio signal and the OBS value set on the instrument how much deviation signal is required to drive the meter movements inside the indicator. As all of this processing is done on the converter board inside the KI209A and uses both the radio signal and the OBS value (which is not available at the GNS in this configuration) our self test cannot drive the lateral meter movements directly.
The Glideslope is connected to signals from the GNS that directly drive the meter movements and as such the self test can drive the vertical needle half up.
You will need to test the KI209A with a regular Nav test set to ensure correct functionality. ”
I then proceeded with the installation and can confirm that my wiring was correct and everything works fine.
Shame they didn’t care to mention this in the manual. Hope this may help someone else in the future!
Interesting.
I did not work out what the issue was, but I am not surprised the GNS does nothing with the composite signal. It is a pretty dumb old box, without any DSP features, so it has a conventional VHF radio (1×COM+1xNAV) and the composite NAV signal is just decoded straight from the VHF. I am sure it will be the same for LOC and GS signals too although they don’t use composite.
