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Car Light Self-Check

Make sure all your lights work without assistance.
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Have you ever tried to give your car a safety inspection? No seriously, have you? Among other things, a safety inspection should include checking that all of the lights come on when they are supposed to. With two people, it is easy enough to have one person in the car to operate the brake, turn signals, etc. while the other stands outside to verify the lights are working. But what do you do when you are alone and don't have a heavy brick to place on the brake pedal?

Build a small light sensor into a corner of each lamp cover. Connect these sensors to lights on the dashboard. When you press the brake pedal, you "see" each of your brake lights come on (but only if they actually turn on). Likewise with running lights, turn signals, and headlights. You don't even need to get out of the car to know your lights work.

BigBrother, Aug 14 2001

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       Absolutely and utterly. It's obvious. It's reasonable. It's practical. It's simple. It's bound to appear somehere else on the halfbakery.   

       Consider also:
1) Detecing that lights work by looking for a continuous circuit. (possibly baked)
2) Using fibre-optics to link back from the lights to the dashboard. (partially baked in that I know someone that retrofitted this to a dodgy tail-light on a motorbike)
st3f, Aug 14 2001, last modified Aug 15 2001
  

       Wot a strowk o' chenius. Of course. Fibreoptics would be the most foolproof, imho. Do it--if nothing else, industrial fleet managers would buy into it to streamline routine safety testing on the company vehicles.
Dog Ed, Aug 14 2001
  

       My '92 Carlton (Omega / Commodore) has this, as did its predecessor ('86 Carlton). The diagnostic unit senses the current running to the bulb; if it's too little, the bulb's blown, if it's too much there's a short-circuit. Also, the rear light housings have a little grille which makes the lit bulbs visible from onside the car (it's a station wagon).
angel, Aug 15 2001
  

       friend #1: "is my left turn signal is working?"   

       friend #2: (staring intently at turn signal) "...yes...no...yes...no..."
mihali, Aug 15 2001
  

       The current-sensing whatsit sounds like a good idea. Here's another way (which ought to be cheaper than the sensor / fiberoptics thing): have a switch somewhere which puts the car into "lamp test pattern" mode, in which it blinks all of the lights in a simple, obvious pattern (say, left-right-left-right). Start the car blinking, then walk around it checking the bulbs.   

       Both my idea and the current sensor that angel mentions only test the bulb and wiring though, not the control switch (what if your turn-signal lever malfunctions? or the switch that detects when you're using the brake?) But this happens less often than burned out bulbs or (in the case of my car) broken wiring, and there are dashboard indicators for some signals which would make that kind of fault more apparent.
wiml, Aug 16 2001
  

       The unit in my car tests the brake light switch as well. When the ignition is first switched on, the unit sends a little jolt down the lighting wires from downstream of the switches, and indicates the result as described. With the brake lights, it performs the test the first time you hit the brake pedal; until then the warning light stays on, so you can tell whether the switch has failed. If the light doesn't come on with the ignition, the light's faulty. If it doesn't go off when you hit the brakes, the stop-light bulb or switch is faulty.
angel, Aug 16 2001
  

       The fiber optics idea is very well baked. My 1972 Caddy had this system for the tail, brake and front marker lamps.
bosco, Aug 16 2001
  

       My 1985 Nissan 200sx has it too, although only for the headlights and taillights.   

       This one looks rather toasty, but I like wiml's light test...
StarChaser, Aug 16 2001
  

       Darn...I was beaten to the punch. Corvettes have had this feature (in the form of fiber optics) since about 1968. I personally own a vette that used to have it...until some foolish prior owner tried to cut the fiber optic cable and splice it with electrical tape). Anyway, it's been done, and it's a GOOD THING. More cars should have this. My 1997 Lincoln Mark VIII has a self check as well. It will check all the lights (upon request) and tell you if there's a problem. I'm not sure exactly what method it uses though.
LymanSS, Nov 21 2003
  

       my 88 supra is a bit different. If you have an out light in the rear, a dash light comes on. I would think that only the rear would warrent a notice due to you can simply look down the road to see if your lights are working or in reflections of truck tailgates (I do that all the time and they don't like my high beams)
88supra, Jul 15 2004
  

       The new BMW motorcycles (like the R1200GS) have current sensing for bulbs. Not only that, but if the brake light goes out, it dims the rear running light, and then returns it to full brightness when you brake, creating the illusion of a brakelight, enough to get you home safely.
phidauex, Aug 13 2004
  

       On my '96 Cavalier, the blinking cadence on the turn signals would change quite noticeably if a bulb was blown. Don't know if there was a special circuit to detect that, or they were simply using a thermo-mechanical blinker.
supercat, Aug 13 2004
  

       That's the old bi-metal strip, [supercat]. The electronic flasher units don't seem to do it.
angel, Aug 13 2004
  
      
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