Garmin 335 XPNDR OAT probe install

[Scott MacMoyle]

In the process of installing my transponder when I noticed it has an OAT probe input. I put a new windshield in my Grumman Tiger and purposely did not reinstall the old turkey thermometer that was used as a handle that required a windshield change so I was looking for an upgrade anyway. I bought a davtron probe. Has anyone done this ? I coudnt find much by way of instructions

 

[NordicDave]

Smartest decision you’ll make on installing a Garmin GTX transponder. That probe will provide real time OAT and density altitude instead of just pressure alt. Mine has proven invaluable.

Also get the GAE12 Alt encoder. Most avionics shops charge the same or more to install the old encoder than buying and installing this one. It also separates your static line from the transponder.

 

[Scott MacMoyle]

does it just use the probe to compute density altitude or does it also display OAT ?

 

[Scott MacMoyle]

got the encoder and splurged for the custom harness. Im an IA so Im doing the install on my own plane. I had an old Narco AT50 in there so this was an easy decision.

 

[NordicDave]

does it just use the probe to compute density altitude or does it also display OAT ?

Yes, all you need is the OAT probe and the GTX will calculate density Alt and display OAT simultaneously. OAT is config selectable for F or C readout. The option for pressure alt display also remains, but on a separate pilot selectable screen.

 

[Scott MacMoyle]

Got it all installed and it works great. I spent the extra time to put the probe out in the wing panel instead of the NACA scoop. Garmin wanted a shielded cable but said I could use a Davtron probe which is not shielded. Davtron said the wires could be extended or shortened without effecting calibration so I extended it and it works fine without a shield

 

[NordicDave]

Awesome! Glad you like it and it worked.

 

[Scott MacMoyle]

yes. just got the flight evaluation out of the way. No red flags. It took me a long time to do this install. I would have lost money if I did it for hire.