Will I be able to drive to work in the morning?

February 2, 2017 5:18 PM

The front dome light in my 2009 Prius won't turn off. Will it drain the battery overnight, and if so, is there anything I can do to prevent it?

Driving home from my son's piano recital tonight, I discovered that the front dome light in my Prius won't turn off, even when I switch it to the "off" position and even when I power off the car and lock the doors from the outside (which usually switches off the dome lights). Assuming it stays on all night, will it draw enough power to drain the battery? Is there anything I can do to force it to shut off? I'd prefer not to have this happen to me. Assume that I know next to nothing about cars, and it's about 20 degrees F here tonight, so I'm not going to be tinkering with it extensively.

And yes, I'm mortified that I've owned this car for over 7 years and don't know the answer to this.

posted by spamloaf to Travel & Transportation (13 answers total)

Best answer: You can remove the bulb until this issue is fixed. You won't have a dome light, but you also won't risk being stranded.
posted by spikeleemajortomdickandharryconnickjrmints at 5:24 PM on February 2, 2017 [6 favorites]

Best answer: Can you take the plastic cover off of it and remove the bulb? It should be pretty straightforward. I don't have a Prius or I'd go look. They usually just kinda pull out. Yes, it probably will drain the battery overnight. The other option would be to disconnect the battery overnight, but I suspect that's complicated in your car.
posted by mareli at 5:26 PM on February 2, 2017 [2 favorites]

there may be an appropriate fuse you can pull to cut power to the bulb as well- check your owners manual.
posted by noloveforned at 5:32 PM on February 2, 2017 [2 favorites]

If you can't do the above, try turning on the headlights to see if you have battery left BEFORE you put the key in the ignition.

I learned the hard way on my 2012 Subaru Outback that if the battery is completely drained and you put the key in the ignition THE KEY CANNOT BE REMOVED UNTIL THE BATTERY IS CHARGED.

I don't know if that is true in a Prius, but you don't want to head off to work and leave your key in the ignition for any thief who might come by with a set of jumper cables.
posted by ITravelMontana at 5:32 PM on February 2, 2017 [1 favorite]

I don't drive a hybrid but I have had this issue and was unable to get the cover of the dome light off to remove the bulb. I removed the fuse overnight, car started fine when I put it back in. Looks like the fuse for the interior lights also controls the turn signals so you may not want to do this if you are not confident in your ability to put it back in.

Edit: the index may be referring to the turn signal indicator inside the car and not the actual turn signals. Not very clear.
posted by skyl1n3 at 5:33 PM on February 2, 2017

Agree with the above - don't risk it, but pull the fuse or the bulb.

My guess is one of the door switches (little push switch inside the hinge area of the door) is stuck, so you can try wiggling those and see if you can get the light to go off. You can see one of those sensors here (looks like a little pin sticking out that you push in to replicate the door closing):

https://priuschat.com/threads/door-sensor-problem.70654/

If you have even the slightest mechanical aptitude this is probably the easiest fix there is. You can change them with a screwdriver and maybe 5 minutes.
posted by Brockles at 5:39 PM on February 2, 2017 [2 favorites]

Response by poster: Update: the light is off, and I'll be able to drive to work in the morning! (Barring, you know, nuclear holocaust or 12" of snow.)

I went back out to the car to try unscrewing the bulbs, and after prying the plastic cover off with a screwdriver, tried to unscrew the bulb that was on. It was hot, though, and while I was thinking through what to do about that (go back inside and get my garden gloves?) I realized that it wasn't actually the dome light that was on -- it was one of the two "personal illumination" lights or whatever-they're-called, that turn on by pushing a button like in an airplane. So, I pushed the button to turn it off and all was well.

I did mark two answers as best because they were the ones that got me out there to look at the thing, and because unscrewing the bulb is (for me, at least) a far, far simpler fix than anything having to do with a fuse. And I'm confident it would have worked had I needed it.

Thank you!
posted by spamloaf at 5:55 PM on February 2, 2017 [6 favorites]

Edit: the index may be referring to the turn signal indicator inside the car and not the actual turn signals. Not very clear.

The turn signals in the car would not be separately fused.
posted by Brockles at 5:56 PM on February 2, 2017

For future readers, the battery on a Prius is (in my experience) incredibly low capacity. Twice we've left a dome light on overnight and twice the car has refused to start in the morning. I now own a portable jump starter similar to the model recommended by The Wirecutter.
posted by jeffch at 7:10 PM on February 2, 2017 [3 favorites]

Agreeing with Jeffch. The dome light will drain out the battery.
Ask me how I know.
posted by SLC Mom at 8:05 PM on February 2, 2017 [2 favorites]

Just an FYI - I know your problem is solved, but you can also get something like this if you turn the instrument lighting dial all the way up.
posted by coberh at 9:50 PM on February 2, 2017

Expanding on jeffch, hybrid cars have much smaller 12 volt batteries, because that 12V battery does NOT have to ever crank the engine. A hybrid's drivetrain has an electric motor integrated with the gas engine, normally used to help propel the car down the road, but THAT same electric motor is used to crank the gas engine. That electric motor uses the "HV" (high voltage) battery that is unique to hybrids (and electric cars); it does not use a classic "starter motor" and does not use the 12V subsystem.

So the 12V subsystem is only needed for accessories, and to keep the brains of the car available while it is parked (i.e. listening for your keyfob, running the alarm system, etc.)
posted by intermod at 10:08 PM on February 2, 2017 [2 favorites]

...while I was thinking through what to do about that (go back inside and get my garden gloves?) I realized that it wasn't actually the dome light that was on -- it was one of the two "personal illumination" lights or whatever-they're-called, that turn on by pushing a button like in an airplane. So, I pushed the button to turn it off and all was well.

I was just getting ready to suggest that it could be one of the lights that you realized was the culprit. As the saying goes, ask me how I know. Glad you figured it out quickly.
posted by Dolley at 5:35 AM on February 3, 2017