Odd Garmin 430W issue - unique to the plane only

[k9medic]

I recently purchased a G430W to put into my rental plane. It was removed by an avionics shop, was bench checked and had an 8130.

My local shop did the install and we had no side tone or modulation when trying to TX. All wires and pins were checked and rechecked and still no change. In this process we figured that maybe the CP126 from 1976 was just not playing well so we swapped is for a kx24 audio panel. When we swapped audio panels you could almost hear some modulation.

I pulled a second, known working 430W from my personal plane and put it in the rental plane. All of the sudden it worked. Oddly though, when I put the rental plane 430W into my personal plane, it too worked.

Everybody is stumped! Needless to say the radios stayed swapped but we are trying to figure out the WHY on this.

 

[AV8R_87]

Bad/dirty contact, either on the main connector or the antenna.

 

[David Price]

bad tray connections, re rack - tighten, try first before spending $$$

 

[Datadriver]

I had the same problem with a 430W. There is a sidetone adjustment buried deep in the config menus. Power on with the ENT key held down, once on turn the right knob to Com Setup, then select Sidetone level.

 

[k9medic]

Found the issue yesterday... UGH.

Spent the night previously reading through hundreds of threads and tracing wiring diagrams on the computer. Got to the plane yesterday morning and met with the avionics installer. He was adamant that the radio board was bad and wanted to try a third radio. While he gathered his things to try yet another radio, I pulled the 430 out and started probing the pins in P4002.

Found that when they installed the 2 power wires into 4002, they missed counted and put the pins in the wrong holes so it was not getting power to the comm side of the radio. 10 minutes later it was fixed and running well.

The avionics tech was a bit humbled. He's been doing radio work for 50 years and simply mis-pinned the plug. He was so certain it was a radio issue that he didn't count the wiring in the plug. I shared with him what confirmation bias is.

 

[AV8R_87]

The avionics tech was a bit humbled. He's been doing radio work for 50 years and simply mis-pinned the plug.

If I had a dollar for every time someone told me "it's wired per drawing, we checked it three times"...

Happens to everyone, glad you found the issue and nothing got damaged in the process.

My method is to always wire power and ground first, check them, then take a break and check them again.

 

[David Price]

"I pulled a second, known working 430W from my personal plane and put it in the rental plane. All of the sudden it worked."

Just wondering how it worked with the incorrect pin wiring?

 

[AV8R_87]

Just wondering how it worked with the incorrect pin wiring?

I'd have to dig in the install manuals, but I wonder if it's a case of one of them being a slightly different part number that combines the two power inputs internally through isolation diodes.

 

[k9medic]

We were wondering the same thing! One radio is a -40. The other a -00

 

[AV8R_87]

It would be interesting to know which dash number worked and which didn't.
The -40 is a non-WAAS unit that has been upgraded. There are some alternate power pins on P4001 that are always present on the -00 unit, but are optional on some of the non-WAAS units.

Pins 15 and 72 on P4001, Aircraft Power 2: Applies only to part numbers 011-00280-30 (GNS 430), 011-00836-10 (GNS 430A), 011-00506-30 (GNC 420), 011-00837-10 (GNC 420A) and 011-00504-10 (GPS 400). For applications requiring secondary or alternate power bus input.