looks like the only Bendix/King CDIs supported are the KI 202, KI 206 and KI 207.
I believe the difference is due to the fact that your 209 is built for the KX 155 radio, who doesn't have a built-in VOR/LOC converter, while the 202, 206 and 207 rely on an external converter, such as the one in the KX 165 or Garmin SL30.
Hello FlyBill, I want to update your answer, and correct VAF Database, so others won't be mis-directed, by the 2006 post.
Here is a link to Aircrafts Spruce website, and under their Q&A section, I will re-quote, what they say, as well as, let everyone know, a Garmin / Apollo SL-30 will work with a King KI-209. It is well documented. http://www.aircraftspruce.com/catalog/avpages/garminNavCom.php
Is the SL 30 Nav/Com compatible with the King KI 209 VOR/LOC/GS indicator?
Yes, the SL 30 is compatible with the KI 209. Our harness is only wired on the Com side as we do not know what CDI you will be using for the Nav.
Is the Garmin SL 30 a suitable replacement for the Narco 12D TSO? Can it use the same CDI or must the CDI be replaced at the same time?
Yes the SL 30 is a good choice for a NAV/COM replacement (not a slide in replacement as a new install is required) for the Narco 12D. It is high recommended that you upgrade the CDI to the Garmin GI 106A.