I think the PC-6 was updated, but for me outside of the Content Manager. 
Yes, the update was pushed during sim launch. I posted an image of my updated products in another thread.
TLDR
I now have the āSteam Gaugeā PC-6 (SG PC6) transponder working.
Edit:
Oh! Now it is not working looks like some sort of intermittent issue
Iām not convinced this is important but it all started to work after I tried doing Cold and Dark Start (CaDS) using āExternal powerā.
TL
The AAU3 update was downloaded yesterday. In preparation for it I had even being flying the SG PC6 and thought if they could get the transponder to work this could be my go-to plane.
So you can imagine my disappointment when I tried a CaDS to find that the transponder did not work. It seemed that this bug had not been addressed. I was disappointed 
I look at the bug report for the problem and @NixonRedgrave had updated it to say the bug had not been addressed. So it was not just me.
I start adding a follow on post to say I am seeing the same problem. Then I think āPerhaps I should check the SG PC6 Ski variantā unlikely as the difference between the two aircraft is the skis. No, same problem. Back to the bug report. Take screenshot showing that some of the transponder buttons do not have their status displayed (N/A is displayed). Then I think āPerhaps I should check if the transponder works when the external power is selectedā. Blow me down sideways the transponder pops into life 
Now it gets strange. When I go back and reset the SG PC6 Wheel I canāt replicate the problem. I start looking for why this might be even to āRestartingā my PC and FS20 but the transponder is working fine. Iād blame some sort of caching issue as I had been using the aircraft before the update but that does not fit with problems @NixonRedgrave was seeing.
I have not checked if the transponder is working on the G950 variant because I donāt get on well with the glass cockpits on my 1080x1920 monitor (or it might just be my eyesight). sPK
Edit1:
Just turned my PC on and booted FS20 to find myself unable to turn the Transponder on
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I tried that and it didnāt work for me with the wheels or skis variants.
I will try it again today with a fresh boot of the sim.
If it makes you feel any better. I have just turned my PC on and the old problem is back (Transponder will not switch on). Iāve not tried any investigaiton. Iām going to the end of the runway with the engine running. An interesting issue with this bug sPK
3 Likes
I booted the sim and loaded C&D in the PC-6 wheels variant and the transponder came to life.
I quit the sim, relaunched, reloaded C&D and it still works.
I quit to the menu, switched to the PC-6 skis variant, loaded C&D and the transponder does not work.
I reloaded into the wheels variant and the transponder is back to not working.
Something is def messed up here.
The indicator lamps donāt work in either of them and the ADF1 breaker does nothing, but the XPDR breaker kills the ADF.
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Every single player benefits when included aircraft are updated. Thereās literally no downside to that.
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A quit of the sim and a fresh load and the wheels variant transponder works again.
There is, at least, something going on when switching between the GNS wheels and GNS skis variants that breaks the transponder in the wheels variant. I have not seen the skis variant transponder work yet.
I still like flying this airplane, though.
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How did the update of the PC-6 actually appear, as after the update, all I could see in the Content Manager were updates for the other 2 aircraft? There was no update visible for the PC-6, so would that have been applied via another route?
When AAU3 was installed, the aircraft was updated via the Update Manager upon first boot.
All I had to update in the Content Manager were the A310 Enhanced & A320neo v2 Enhanced ā both of which are optional content downloads. The base A310 & A320neo v2 were updated on first boot as with the PC-6.
2 Likes
Ha! I didnāt even know that existed! Downloading now 
1 Like