The Mystery Bubble Finally Bursts

You’ve probably seen the dashboard bubble. It’s a tiny plastic dome mounted near the bottom of the windshield. Many late-model cars have it.

On our curiosity meter, the dashboard bubble ranks somewhere near whether this morning’s cup of Starbucks was “fair trade” or, um, unfair trade.

It’s a nagging sort of curiosity. Is it a signal point for remote keyless entry? Does it facilitate better radio reception? Does fair trade brew taste any better than the normal stuff? Whoops, wrong subject.

We checked it out.

Comments

I used to have an Olds Achieva with daytime running lights (DRL) that didn't work correctly. ALL the lights stayed on, day or night. The sensor was hidden in the defroster vent and could only be replaced by removing the entire dashboard to get to the wiring, which the dealer refused to do. After many trips to the dealer proved unsuccessful in fixing the problem (they replaced everything BUT the sensor!), I finally fixed it myself. I popped off the cap covering it and reamed out the little hole to let more light onto the sensor. Problem solved. Who needs stupid DRL's anyway??? Way too many gadgets in today's cars.

The theory behind daytime running lamps is they make your car easier to see during the day -- especially helpful on two-lane roads if other drivers aren't paying much attention. Of course, if everyone has them, drivers aren't as likely to notice.

Were DRLs mostly the provenance of American cars, or am I just insufficiently worldly? (None of my Toyotas have ever had them.)

I see your point, Kelsey, but I disagree slightly; I'm thinking about the distinction between "noticing" and "paying attention". DRLs make a car visible at a greater distance, and my intuition (and a little schoolin', but that's a bit distant) is that a portion of the brain will notice the headlights and think "car", if not at least "object", whether or not the driver pays conscious attention.

Yes. If you put an opaque object over the light sensor, it will do whatever it does when it is dark. (e.g. turn on the headlights)

For whom was this bubble a mystery? Even if it weren't in the owner's manual, it's a pretty short train of thought from, "Hey, what's that bubble on the dash?", to "I wonder if that could be the light sensor." to putting a book on top of it and watching the headlights come on.

Kelsey M, writes that if everyone has DRL we won't notice them. DRL have been mandatory in Canada since 1991 and trust me they make a difference. There are a few cars on the road which don't have them (disconnects, american cars, old cars ...) and they really lack visibility-even in bright sunlight.

First, a subtle clarification: The bubble is not for DRL's (Daytime Running Lights), but for automatic headlights (in old GM-speak, twilight sentinel). These systems turn the headlights on automatically based on ambient light conditions. DRL's stay on constantly, using a second filament in only the high-beam bulbs.

My car has DRL's, but not automatic headlights. Hence it has no such sensor. My friend's Pontiac of the same vintage has automatic headlights, but not DRL's. Her car therefore does have a bubble on the dash. [I should point out that the front-and-center bubble is most commonly used on GM models. Other companies have found more discrete placements for these sensors.]

Second, Luke says no Toyota he's ever owned has had them. Our company uses 2004 Camrys as fleet cars, and they have a special position on the headlight switch (on the signal stalk) marked "DRL." It allows the driver to enable or disable the DRL (not automatic headlight) function.

MY WIFES BUICK HAS DRL BUBLE AND DURING DAYLIGHT SHE CANNOT READ THE DASHBOARD AS ALL LIGHTS ARE OUT. AT NITE IT IS LIGHT UP LIKE A X-MAS TREE. THE DEALER STATS THIS WAS A ENGINEERING GOOF. PLEASE SOMEBODY HEAP HER.