Disable hyperflashing / fast turn signal flashing on early cars.
 

If you've converted your turn signals to LEDs, the best way to deal with the fast flash / bulb out warning ("hyperflashing") is to disable the bulb checks using NCS Expert. Unfortunately, the option to disable bulb checks isn't available on earlier cars. You can add load resistors, but this is annoying, inelegant and melts things if you're not careful. There must be a better way, and indeed there is - if you are comfortable with surface-mount soldering.

The early BC uses a collection of Motorola MC33286 high-side switches (essentially electronic relays) to switch power to lots of things, including the turn signal bulbs. The MC33286 is pretty smart; it can detect short circuits, overloads, open loads, etc. and it reports some of these (open load in particular) back to the CPU in the BC by pulling a pin low.

Fortunately, the circuit in the BC that monitors these pins is pretty simple. There's a resistor that pulls the pin high, and another resistor between the pin and the CPU. We can re-arrange these resistors so that the CPU pin is pulled high, and the open load signal is disconnected...


https://cimg7.ibsrv.net/gimg/www.nor...39335e1ac.jpeg
Series resistors (circled) already removed.

The two MC33286 devices marked R and L are the ones that handle the right and left turn signals respectively. We only need two of the four resistors, so two are removed, and then the remaining two re-arranged to pull the CPU pin always high:


https://cimg7.ibsrv.net/gimg/www.nor...46aed5646.jpeg
(sorry about the poor focus on the second shot, need another coffee... also clean up your flux...)

And that's it. No more being mistaken for a teenager in a Civic...

That must've taken a lot of investigation and I'm very impressed with your engineering skills!