The RC9, RC20 & RC25 are all the same design and use the same repair kit
The RC18 & RC38 are very similar as far as installation. The main difference is RC28 has a standard rubber keypad and RC18/38 uses a plastic snap dome with conductive ink. With RC28 the rubber seeps oil and loses conductivity. In the RC18/38 the silver ink scrapes off after a lot of use.
NOTE: the -27 or -40 at the end of the model is the remote frequency (different FCC regulations for countries) The design and keypad are identical, the only difference is the crystal oscillator 27mHz or 40mHz
The #1 issue with Bose ButtonWorx™ installations is customers who have dead Bose remotes. The buttons are fine, the remote doesn’t work!
Since these are 100% radio signal, no IR light and unfortunately no indicator LED, it can be quite difficult for the end user to know where a problem lies. A basic rule of thumb is that buttons fail from heavy use. If your power and volume buttons are a pain to use but some other buttons you hardly ever use still work THEN you have bad buttons. If ALL your buttons stopped working one day or ALL you buttons work sometimes and not other times then you have a BAD REMOTE or worse, a bad base radio.
If you are wondering if your power button is bad or the remote is dead… turn your radio on manually and see if the AUX button works (or some other button you hardly ever use).
If your remote works up close but not far away then you have a broken antenna. It could also be a mess of wires in the back of your radio. The base uses the power cord as the antenna for receiving remote signals.
If your buttons work after repeated pressing then you could have a failing antenna with a crack in the wire. Vibrations from pressing buttons can wiggle the antenna and cause the signal to be blocked or make it through.
For the RC18 and RC38 (OR other models that have been repaired with conductive paint in the past) it is possible for some conductive ink to flake off, stick in a button and confuse the remote into thinking you are holding a button down all the time. That will stop all other buttons from working… suddenly… just like I told you could not happen from bad buttons. It’s rare but possible…. so if you have the RC18/38, one troubleshooting step you could take before ordering a repair kit is to clean the circuit board button contacts really well with isopropyl alcohol and see if the problem goes away. Unfortunately it will be temporary. Once the ink starts to flake off it’s going to happen more quickly and repeat the problem.