I was talking about the traditional generic mechanical turn signal flashers you can still buy at auto parts stores. They don’t work with LED turn signals because they rely on the heat of current flowing to cause the bimetal strip to heat up and “click” to the next position. I know that for a fact, the hard way, by putting LED turn signals on an old-school motorcycle that had one of those in an attempt to get brighter turn signals that used less power (the magnetos on those old motorcycles were so lame that the headlight actually dimmed slightly in time with the turn signal coming on!). I had to swap the bimetal mechanical turn signal flasher out for an electronic one instead.
Many of the newer cars are like my Jeep Wrangler, that uses a CAN bus for all the steering-wheel switch gear that just sends messages to a control computer under the hood to actually turn power on and off to things. Any relays, whether mechanical or electronic, are under the hood (note that it depends on how much current is being pulled as to whether a mechanical relay is cheaper than an electronic relay… for 15 amps to the headlights a mechanical relay is cheaper, but my Jeep uses an electronic one because it modulates the headlights for Canadian daylight running lights via pulse-width modulation and mechanical relays can’t handle that duty cycle). Even the overhead light is controlled by that computer, there’s a widget to plug into the OBDC port that among other things sets parameters in the computer to do different things with the overhead light (like not turn it on when the doors are off, something you do in a Jeep) and if you leave a door open for half an hour or leave the dashboard light switch on for more than that the computer helpfully turns the light out for you to avoid running down the battery. Things like steering wheel radio controls wouldn’t be easy to implement in the cramped confines of a Jeep Wrangler if not for the CAN bus.
Finally: Lion, you’re right that removing the radio won’t cause the car to die (otherwise stereo thieves would be disabling cars left and right when they steal the OEM radios), but most cars since the 2006 model year have had a CAN bus for the dashboard running gear due to a change in the OBD2 requirements that require CAN at the OBD2 port and simply replacing the stereo won’t turn on the amplifiers for the speakers, resulting in a mute car. My Jeep is like that, you have to put in a CAN adapter to tell the Jeep to turn on the rear amp for the subwoofer when using an aftermarket radio, then train the Jeep to recognize that CAN adapter using a strange sequence of switch gear manipulations (basically toggling in binary data like on old-school computers from the 1960’s). The reason why your old school auto mechanic doesn’t know about things like that is because he is like most old school auto mechanics, he is a total electronic ignoramus, and he doesn’t switch out car stereos. He doesn’t see mute cars because car stereo places won’t switch out a radio unless there’s an adapter available for it, or unless it’s an older car that doesn’t need an adapter, and self-install places like Crutchfield publish whether there is an adapter for your car and whether one is needed. Regarding the turn signal flasher, the “click click click” is from a tiny speaker under the dashboard (on my Jeep the same one that goes “ding ding ding!” if you open the door with the key in the ignition) or from a tiny speaker embedded in the “flasher” itself, not from bimetal strips expanding/contracting and causing a relay to flick to the next position. That is true of virtually every modern car, which is why you never hear of people having to change out turn signal flashers anymore – the electronic ones don’t fail the way the old mechanical ones did. Not during the ten-year life of the average car, anyhow. Reducing warranty claims is a goal of all manufacturers now, and with today’s longer warranties, the electronic ones are worth the extra cost to them.
