GNS430 to GTX335

[Mkruger2021]

Installed these two components and I’m having issues with the transponder not receiving the altitude….I pinned a rs232 feed for the altitude but it’s still not receiving.

1. Does anyone have the settings for the GNS and GTX in the setup mode.

2. Are they compatible? (Spoke with Garmin- They mentioned I needed to take it to a Garmin dealer and have them program with a laptop) Not sure I believe that!

Thanks for looking….Matt

 

 

 

[Mkruger2021]

I meant the GPS not receiving the altitude…..

 

[201Mooniac]

I'm not sure but I believe you need both an RS 232 and an ARINC 429 connection between the GTX 335 and the GNS 430.  The altitude probably is a label on the ARINC 429.  I think you might be able to do the configuration of the GTX 335 without a laptop but I know my installer used one when configuring my GTX 345.

[Mkruger2021]

Ok. I may have wired the the ARINC 429 per the interconnect diagram ….ill take a look again. Thanks for the info about your installer….Maybe there is some truth to the laptop…..Jesus, leave it to garmin!

 

 

[Old Chub]

Not exactly the same but I have a GTX 335R hooked up to a GTN750 and I had to take the remote box (335R) to a garmin dealer to turn that function on so the GTN would get the pressure altitude data from the transponder.   I had the pressure altitude going to the GTX335R and the GDL-88 all in the back of the plane.  For the 335R to talk to the 750 its only RS232.  

[skykrawler]

On 6/5/2025 at 1:52 AM, Mkruger2021 said:

Ok. I may have wired the the ARINC 429 per the interconnect diagram ….ill take a look again. Thanks for the info about your installer….Maybe there is some truth to the laptop…..Jesus, leave it to garmin!

 

 

Unless all you have is grey code.....why don't you just connect the altitude encoder directly to 430?

[rklems]

What is your pressure altitude source? Is it a GAE12 attached to the transponder tray, a blind encoder (serial or grey code), or some other air data source? There are many ways to get pressure altitude to the GNS, but the best way to do so is going to depend a lot on what the actual canonical source for the pressure altitude is.