Lights will not turn on? Any ideas?

My headlights stopped working randomly the other day. Kind of a problem lol. I figured it was just bulbs but those are relatively new, replaced within the last year or so. The high beams will not work either. Which is typically not the case when bulbs go out. I checked fuses but all look good and I find it hard to believe all 4 would pop at the same time? I have no other electrical problems that I am aware of.

 

First thing I’d do is take a meter and see if you have 12V at the bulb sockets.

 

Try digging through this. Dude knows is stuff.

https://www.tacomaworld.com/threads/2nd-gen-information-diagnostics.784008/

It’s highly unlikely to be the bulbs, generally a failure will present as one function of one bulb, like low beam on one bulb, not low beam and high beam on both.

When you turn the switch on, do the rear running lights come on?

Someone who knows more than me will eventually respond saying check this specific fuse or relay or whatever.

 

I checked power with a multimeter and everything looks good. 12.4V at the low beam and high beam connectors. Which is a good sign I guess?

 

Check the ground at the connectors but it would seem you just have blown bulbs.

 

I’d try some new bulbs

 

Sounds like you have a multimeter. The connector is 3 prong. Now that you know which is ground, test the bulbs. Ground to one, then the other one, both should have continuity. If both bulbs pass, you might not be getting a good connection between the connector and bulb. Or like Dm93 suggested, bad ground.

 

Well on a whim I decided to just buy a cheap set of 9003 bulbs and try new bulbs. I swapped them and the flicked right on! I dunno how all 4 bulb settings (low/hi on both sides) popped at the exact same time?

 

Are the headlight housings getting water/moisture in them? That would certainly blow the bulbs in short order.
Also be careful not to touch the glass part of the bulb with your hands when installing them as that can shorten their lifespan.

 

Check the ground. Connect your multimeter, move & wiggle the wires watching for a spike in resistance.

I’m wondering if you’re getting a problem from a failing alternator, possibly not regulating & voltage going too high.

All 4 functions failed at once I’ve never heard of but I guess not impossible, like getting 4 flat tires all at once. Anything odd like multiple batteries for bouncy hydraulics?

 

I've seen it several times, I had a car come in one time that had 7 bad bulbs so I never discount bad bulbs lol.

 

Does the headlight indicator on the dash come on.
That's "kind of" a good way to see if it's a power issue.
Not definitive. But the LED in the dash doesn't usually go bad.

At least, that's one check I'd do first. That will steer my direction.....

 

Hmm a while back I was getting a flickering battery light indicator on the dash. It would flicker randomly for a couple weeks but I never noticed any dimming or hesitation like the alternator was failing so I didn’t think anything of it. I haven’t seen it in a couple months? My alternator was replaced in 2015 or about 40k miles ago.

is there a reliable way to see if the alternator is failing? I test voltage at the battery and it’s still reading 12V

 

Yes it comes on for both high and low beams.

 

Did you test the voltage with the engine running? I second the possibility of a faulty regulator.

 

I just rechecked with engine running and it was steady at 14V, I assume that’s too high right? I figured if alternator was failing that voltage would be fluctuating?

 

No. 14v isn’t too high.
Mine gets there sometimes.
Most of the time, mine is at 13.6-13.8.
But it hits 14v too….

 

Anything from 13.2-14.8v is fine for running voltage on a 2nd gen.

 

Okay that’s good to know. I’m assuming I just got unlucky with bulbs at this point.

 

Just to rule out the voltage regulator, was the voltage steady at 14 when revving the engine? If it increases beyond 14 while revving, the regulator is bad and the alternator (internal regulator) needs to be replaced.