Dear colleagues, does anyone of the KLN94 GPS experienced user here know if I can substitute a broken KLN94 with roll steering (s/n: 069-01034-0102) with a
non Roll Steering KLN 94 (s/n: XXX-XXXXX-0101) only by doing a software update from Version 0101 to 0102 by an avionics shop or does this require some adiitional extensive hardware change?
@wigglyamp will know for sure.
AFAIK there is no hardware change but could be wrong. I never used this KLN94 roll steering and there are posts here suggesting it works poorly. I would be surprised if your plane had that feature connected.
AFAIK, it is not ARINC 424 roll steering and only works with the KFC225 autopilot and even then it does not work well. I would not invest in any updates to the KLN94 and replace it with a WAAS GPS such as the Garmin GPS 175 if you wish to add features.
From my point of view, Garmin does not offer a really satisfactory partial replacement solution for individual components in older avionics stacks with Bendix/King parts, aside from the aspect that most the items are old but working rock solid and reliable.
For that reason I would better renew the whole stack if I need a Christmas gift, but from the a.m. opinions it seems that I can only replace a roll steering capable KLN94 with a unit that offers the same aspect, right?
A Q to Peter: It makes me doubt if you are correct that my KLN94 doesn‘t really manage Roll steering – which I thought it would do in the past? Is there a routine how this could be checked in a quick manner?
I am not sure you can easily tell.
AFAIK the KLN94 “roll steering” works only with a KFC225.
What year and S/N is your TB20? The Socata wiring diagrams contain a S/N range. I am fairly sure that Socata never connected it up, because my TB20 is one of the last TBs made, in 2021.
Well I „thought“ it would operate roll steering, it‘s one of the last TB20s, s/n 2205 of it‘s kind still equipped with a KFC225 🤔, but not sure how to check this out as you mentioned most of the a/c owners would not know about that feature and how to check the roll steering commands being executed to reassure roll steering works as it should?
I have never met anyone who really knew if he had this connected, let alone anyone who collected flight data on the turns. I suspect it never was connected.
The KLN94 – KFC225 always performs “steering”. Each time the KLN94 switches to the next track section, the autopilot follows it. The KLN94 has a setting called “turn anticipation” and this works pretty well. See track examples here.
Proper roll steering (via ARINC429) transmits roll angle commands to the autopilot and this works better. See e.g. here here and here.
As regards who can do the firmware upgrade, a Honeywell dealer should be able to do it. However I suspect most of them have chucked their HBK gear in the bin years ago.
The KLN94 MM is here. It makes various references to the roll steering output. The steering output is here
and I see no reference to it being present only on some models. I suspect every KLN94 has it. @wigglyamp will know, if he is still posting here.
OK, I will check if it in operation if the wiring 
exists. However when purchasing a used KLM 94 it´s not a problem to upgrade the software from V.-01 to V. -02.
It can be perfomed with the Data Loader program which I have to update the databases.
Could anyone help me out in getting the p__/n 222-30469-1001 = KLN 94 CD-ROM__ for Software 0201?
Finally it must be checked it has perhaps to be switched on in the Maintanence program of the KLN 94.
I suggest you contact Avionik Straubing and see if they have access to the upgrade software. They are one of the very few remaining BendixKing repair centres in Europe.
