Hey guys

I was pulled over last night due to not having the taillights on during the dark hours which I was not aware of prior to being pulled over.

The question is that when I step on the break, taillights both light up fine, but they are off when headlights are on.

If it is a simple matter, I'd rather fix it myself rather than taking it in.. Mine is an 04 350z by the way..

Please give me some suggestions if you have any idea on this matter..

I thank you guys in advance!

 

1. Check to ensure bulbs are not blown (brake light part of bulb may still work, taillight part of bulb might be blown)

As you can see, bulb below is like ours and has 2 filaments (thin metal coils inside bulb) one for brake light and one for taillight. One may work even if the other is blown. (To see if one is blown, look for black marks on inside glass and a split filament)

This is NOT a pic of our actual bulb.


2. Check fuses for tallights and brake lights.

 

Thank you for your reply!

I will try as soon as get off work!

 

+1 i'm going to bet it's a blown bulb. check it out and if it's black or hazy inside then replace it

 

sound like blown bulbs. but if both are out at the same time then there might be something else. usually just one bulb is out. get a jdm tail lights. it only costs around $250 on this forum. search the market place

 

You've got a grounding problem in your taillights.

When it's working properly, current flows from the brake switch to the brighter filament in the bulb, and them to ground. Since the ground is now open, it continues through the other filament, then through the wiring to the parking lights, and then to ground.

When the headlights are on, the other filament has 12 volts on it, so no current flows through the brake light filament.



There's some more info here:
http://www.ehow.com/how_4827501_bad-...ke-lights.html

 

^ I doubt that. Prob blown filament.

 

Read the original post:

"...when I step on the break, taillights both light up fine, but they are off when headlights are on."

I'll bet that if you look very closely, you'll see that it's the filament for the rear parking light that is lighting up. It draws less current than the filament for the brake light, so it's going to light up with a bad ground situation.

 

Na bruh, i think he's saying the brake lights work when he steps on brakes with lights both off and on. But when lights on (only time taillights come on) the taillights dont work. hinting at the taillight filaments might be blown which you could only tell with lights on.

Still, you could be right, however a blown filament is the much more common issue and should be checked first. Then fuses, then possibly electrical problems like your proposing.

Its the order of things brovlosky. If it isn't blown, and OP has any brain matter, he'll come back in here and inquire into more options.

 

The tail lights weren't on because there is no ground. The brake light filament goes back to the brake light switch, and it's open when the brakes aren't on. If there's no connection to ground and no path to ground some other way, the tail lights won't come on.

Look at the circuit above, mentally disconnect the ground at the bottom of the light under A7 and/or A8, and see how the current will flow. You'll see what I'm talking about.

 

K, we will wait for OP and see what he found out.

My cash is on busted bulbs.

 

sup guys

thanks for all the great info.

it was actually the blown fuse with blown bulbs..

fuse was the one behind the battery on the very top (10A, i think)

and yes.. i also had 2 blown bulbs..

so i changed all 3 of those and it's working fine now.