Electrical demons!

Good morning all!

I have a 1993 sport, 4x4 4.0HO with ~120K on it, auto trans.

Backing up into a parking spot today (with my lights on) i catch a reflection of my tail lights. The driver's side brake light is always bright on, doesn't matter if brake light is depressed or not. My passenger side brake light is dull (almost can't see it) until the brake is depressed, then it gets bright.

Now if the headlights are off it is like the exact opposite. drivers side brake light is very dim until the brake is depressed, then it is bright. The passenger side is bright until the break is depressed then dim!

I have an FSM, but it's at home and i am at work, can someone advise how they are supposed to work under both conditions (headlights on or off?).

i should note that my NSS is bypassed right now due to me breaking the crap out of it when i tried to clean it due to no-start issues. I also replaced the driver side brake bulb yesterday due to my neighbor saying the brake light was out.

Thanks!!!

sounds to me like you may have a ground issue? or possibly the wrong bulb installed,

when the brake pedal is pushed the bulbs should be bright, headlights on or off makes no difference

when the headlights are on the bulbs should be dim then bright when the brake pedal is pushed.

hope this helps

maybe you replaced the bulb with single filament instead of dual filament

i will have to check my grounds tonight, i replaced it with a 6047LL bulb (i believe) b/c that was what was already there and that could just as easily be the incorrect bulb. i will have to check that as well.


also, with the headlights on and the bulbs bright, do they get a bit brighter when the brake is depressed?

thx!

yes your brake lights still come on even when headlights are on! the bulbs are dual-filament, one for running lights, the other for brakes.

I'm betting the ground for the affected tail light is bad, resulting in backfeeding through both filaments when either one comes on. Could be wrong though...

ground is constant for all bulbs in the tail-light, it's a power bleed

ehall said:

ground is constant for all bulbs in the tail-light, it's a power bleed

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You are right, i wasn't clear above about the wrong bulb, but that is what i was thinking, that he put a single element bulb instead of the dual element

1156 Rear turn
2057 Tail Light
2057 Stop light
1156 Backup light

1993 Jeep Cherokee per Sylvania application guide.

Take out bulb. Look down into the socket. If it has two titties OO down there, it needs to have two titties OO on the bulb. If you put in a bulb with one titty O it can make the running light and brake light circuits common. You also had to force one of the little side titties past the slit in the socket. Dual filament bulb has one deeper and one shallower titty on the side of the bulb. Single filament are both deeper.

winterbeater said:

Take out bulb. Look down into the socket. If it has two titties OO down there, it needs to have two titties OO on the bulb. If you put in a bulb with one titty O it can make the running light and brake light circuits common. You also had to force one of the little side titties past the slit in the socket. Dual filament bulb has one deeper and one shallower titty on the side of the bulb. Single filament are both deeper.

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I KNEW you were a dirty old man! ROTFLMAO! :roflmao:

LOL, thanks for the input all. HAHAHAAHAH.

made me think, since this is the bulb that i just replaced, could i have put it in incorrectly? the high filament seems to work fine (and all the time when the head lights are on), but it doesn't work at all when the headlights are off.

i didn't get a chance to check tonight b/c i got off of work so late, but i did at least use the correct bulb! 2057 so tomorrow morning hopefully i can take a look at it...

joe_peters said:

1156 Rear turn
2057 Tail Light
2057 Stop light
1156 Backup light

1993 Jeep Cherokee per Sylvania application guide.

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Sounds right to me, however i rarely use an 1156.
A dual element bulb (2057) can be used in place of a single element bulb (1156) but not the other way around.

Update -

So i took the tail light apart again and got to the socket and bulb, i found some corrosion which i carefully cleaned off with a dental pick and also realized that the bulb his a high nub and a low nub. i lined up the nubs in the socket and everything worked again.

So know i know to pay attention to bulb alignment in the socket! lol.

hightime81 said:

Update -

So i took the tail light apart again and got to the socket and bulb, i found some corrosion which i carefully cleaned off with a dental pick and also realized that the bulb his a high nub and a low nub. i lined up the nubs in the socket and everything worked again.

So know i know to pay attention to bulb alignment in the socket! lol.

Click to expand...

The Devil is in the details. :firedevil

I did that on my first car, I figured it out when the headlights came on every time I applied the brakes.