Instead of replacing the head unit of my car I decided to rather just get an FM Transmitter. I ended up with a cheap one from ebay, one that looks like this. It has a USB port to charge things from and a 3.5mm male audio jack to plug into MP3 players, cellphones etc. The only problem, is that the cigarette lighter in my car is located just infront of the gear lever, this gets in the way and the wires there annoy me.
This got me itnerested in building it into the car. I eventually decided to make use of one of the “button” covers in the row of buttons. I have two blanks, so went about mutilating it to achieve my goal. It wasn’t as easy as I had hoped, the blank has a hole lot of junk on the back, but I sawed and ground it off to be left with just the right amount of space to mount a button, a female 3.5mm audio jack and an indicator LED.
I trimmed the power lines going to my radio just behind it, and added two connectors so I could easily plug in and remove the fm transmitter if need be. It’s more convenient and also a bit safer/neater than soldered wires all over the place.
One unfortunate thing, is the way I put everything together, it required me to push the FM transmitter through the hole of cover. This was problematic as it was too large. In the end I discarded majority of the case, and wound some insulation tape around the circuitry just to protect it. Not what I had wanted, and not particularly neat, but it works.
Hooked it all up and it’s up and running. The FM transmitter is a cheap one, not that great quality and only transmits on 2 set frequencies, but it does the job. I have found however that the 5V it supplies for USB isn’t that great. My GPS doesn’t seem to like charging from it, although my cellphone is fine. I think the current may be rather limited, so may look into repacing that part of circuitry at some stage.