auto off dome light?

More than once the dome light in my WRX was accidentally left on and almost killed my battery.

Is there a way to modify it so that the dome light turns off after, say, 15 minutes? Or replace the bulb with a LED-based light?

Reply to
james
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There are LED festoon bulbs for dome light replacement.

I looked at them some months ago but procrastinated and didn't proceed because I wasn't sure about the auto-dimming when the door closed. The question I never got around to answering was, did the present incandescent bulb dim because of reducing voltage or reducing current, and would the LED work the same or be destroyed.

I know just enough about electricity to be dangerous.

Reply to
Bugalugs

If the bulb dims, it means that the voltage across it is reduced, causing the current through it to be reduced If the LED bulb works at full voltage, it will not be damaged when the voltage falls.

(I have no specific knowledge about these bulbs aside from owning a few flashlights using them. But the general principle is valid.)

Uncle Ben

Reply to
Uncle Ben

It's fun, isn't it?

Except having a recurring twitch from being zapped too many t-t-times...

Reply to
Hachiroku

The LED based bulb still uses 12V. There is a voltage-drop resistor in there that drops the voltage to 3 or 5V depending on the LED, but to the overall circuit it still looks like 12V. It ain't helping on current, either, because the resistor may actually be drawing more current than the OEM bulb is.

Reply to
Hachiroku

Hi, May I be differ? LED current consumption is way less than a bulb. In the range of miliiamps. Resistors main job is to drop the voltage at that current draw. Overall LED will use way less energy(literally no heat). Refresh your high school physics; Ohm's law. Look at the size of resistor which is typically less than 1/2 Watt size which means?..... I replaced all the illumnation on my patio in the back yard with LEDs. They consume 1W each vs. bulbs which is ~7W and up.

Reply to
Tony Hwang

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The 12V LED bulb (which is an assembly with an internal regulator) would draw less current. That can affect any flasher devices that rely on the current draw, like the old flasher units with bimetallic strips that rely on heat to flex the strip so the current draw determines the rate at which they heat up and if they heat enough to flex to make connect (whereupon they cool and flex to break the contact). Timer circuits don't care about the load. Even with a blown bulb (i.e., no load), the circuit is still timed.

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You didn't specify the year for your WRX so you'll have to search yourself. Once you used the Sylvania site to identify your bulb, you can then find out what LED replacement to use. For example, if it is a DE3175, go to the superbrightleds site and look in the cross-reference list to see that you need their 3022 model, a festoon style bulb. You can even pick a color. They have some high-power models but even those probably won't put out as much light as an incandescent bulb. I didn't see them list how much current they draw (plus you would have to find out how much the incandescent model draws to do a comparison).

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I suspect you don't want to actually build the thing (etch a PCB, solder the components together, put into a box, splice into the dome light wire, run a wire to a constant 12v source). You might know someone that can fab this for you.

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This has the advantage of not only turning off the dome light when you leave but leaving the dome light on as you enter (so you can see where to push in the key for the ignition switch, for example). However, 5 minutes would be way too long to leave on the dome light when you entered the vehicle (or anytime you opened the door). With some more Googling (which the OP should do), I'm sure other units are available that can perform a similar function but be more appropriate for dome light timing that for cargo light timing. I'll let you do the Google searching.

You sure there isn't a timer for the dome light? From some articles, like:

http://74.125.113.132/search?q=cache:c7o2Y6ryzBQJ:

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?q=cache:z6dHLoxon2EJ:tmj4.carsoup.com/new-vehicles/makes/Car-Truck/Milwaukee/Subaru/Impreza-Wagon-WRX/2009/2009472533/+%2B%22dome+light%22+%2Btimer+%2Bwrx&cd=9&hl=en&ct=clnk&gl=us A timed dome light feature is mentioned. Maybe you have the switch on the dome light in the wrong position. Maybe it's not included unless you get some trim package, but that would mean the part is available (but probably rather pricey from the dealer's parts store). There appears a "On w/Open Doors" setting as mentioned at
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Could be thetimer went bad (so you might get it replaced under warranty). Could bethe rubber boot around the door switch is crinkled up and keeping thedoor switch pressed down (which keeps the switch in its open or breakcondition). Does the dome light come on when you open the doors? Youcould also look at the dash to see if a door is shown as open when youopen it (and the ignition key is on). You could just forego the dome light and leave it off all the time. Then just turn it on when you need it.

Reply to
VanguardLH

Some configurations require a resistor in *parallel* to increase the current draw. If you use LEDs for turn signal bulbs, you may have to include a resistor in parallel for the flasher unit to work. Older thermal-based flashers require a minimal current draw to heat their bimetallic element that heats up to make contact and cools after making contact to break the contact. In fact, the age-old problem of hooking up trailer lights was the flasher would blink too fast because more current was drawn through the thermal flasher unit which made it heat up faster. See

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A loadresistor to increase current draw obviates the advantage of less currentdraw for an LED.

If a timer does not rely upon the load to affect the timing then using an LED in place of an incandescent will work (i.e., the circuit is timed even if the bulb is blown). From what I've seen, dome light timers are load dependent. Also to consider is that LEDs put out less light than incandescents. That means you need more LEDs to generate the same lumens as an incandescent. LEDs are directional in their light output so a diffuser lens is needed or multiple LEDs need to point in multiple different directions.

From what I read, the WRX should have a position for the dome light that provides for an auto-delay shutoff. Perhaps the dome switch is in the wrong position.

Reply to
VanguardLH

If the dome light is being left on, that ,means someone turned it to the "allways on" position - so an automatic time-out system would not help. If you can't learn to shut off the domelight when leaving the car what you need is a "battery saver" system that monitors the battery voltage and shuts everything off when it gets below a certain point - which is still enough to start the car..

These units are available from many automotive mass merchandizers, like Canadian Tire in Canada.

Reply to
clare

Especially by the sparkplug wires !!!

Reply to
Bugalugs

Mine has a 3 position switch. I interpreted the OP to mean the light was inadvertently left on instead of being put back into the center position.

Carl

Reply to
Carl 1 Lucky Texan

Correction:

Should've been "independent".

Reply to
VanguardLH

Oh yeah! Find a bad plug wire in no time flat!

Reply to
Hachiroku

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