I've been busy for much of the week but I finally got around to it on Friday.  For Christmas, one of  several gifts I received was an RC car.  I noticed it had functional headlights, but the taillights weren't lit.  Of course I opened it up as I've been doing ever since I was a child.

Two things immediately stuck out to me.: the use of a 3 pin connector to connect the LEDs on the car body to the PCB as opposed to a 2 pin connector and  there were holes in the taillights for inserting 3mm LEDs. I probed the 3 pin connector and determined that the middle pin was ground. I then of course put the car in reverse and checked the unconnected pin. Sure enough, it was putting out a voltage.  This car was in fact originally designed to have lighted taillights, but for some reason they were excluded.  

I figured it would be easy enough to fix that. I got a pair of 3mm red LEDs, a pair of 220 ohm resistors,  some wire, and went straight to work.  I probably could have forgone the use of resistors as from looking at the PCB, it appears that the existing LEDs are directly driven from an IC, so probably there's some constant current driving, but I wanted to be on the safe side as I was unable to tell for sure.

For connecting to that third pin, I didn't want to solder directly to the PCB. I had some square female pins meant for .156" header pins.  It was a bit on the large side, but it fitted the connector. I wouldn't have done that for a high current connection, but it's not a big issue for some LEDs that drawl very little current.  I used a LED in the existing wiring to tap into ground. I decided to test it before hot gluing it into the body.  Worked just fine.

I then hot glued it into the body and resembled everything and looked at the final result.  The plastic for the taillights is completely clear, so there's no diffusion which means the taillights aren't fully lit up and makes it obvious what the light source is as shown below. Doesn't make for a particularly great effect.

The taillights are also hard to even see while controlling it while standing up.  This likely explains why the LEDs for the taillights were excluded. This makes it one of those projects where the journey is better than the result.  It got me to be a little creative, fire up my soldering iron, and have some fun.