mayjah

Recently replaced all brake lights/tail lights on our '91 LS400. All new lamps. Tail lights, turn signals, and hazards all work great but no power to all brake lights. Checked brake light fuse, checked brake switch at brake pedal. Checked left trunk hinge, doesn't look like any wiring is frayed or pinched.

Any other suggestions before I take it to the mechanic? Really trying to avoid that, at this point.

LiCelsior

iTrader: (32)

PLEase search for trunk harness, and check www.lexls.com

python

iTrader: (4)

there is a box located on the left hand side of the trunk under the hinge, if u dont have any broken wires by the left hinge, then that box needs replacing

Bali26

Having the same problem as OP. Brake lights don't work. All other lights work fine. Bulbs are fine.

Only one fuse for brake lights under dash as far as I know. Its intact.

Checked brake pedal switch. Its working ok. Park release clicks like it should.

Trunk hinge wires look ok. How do I test them? What about the small box next to it (says lamp failure I think)?

Is there a brake light relay?



Thanks for the help.

Yamae

There isn't any brake light relay.
You definitely need to check the "brake light failure sensor" located in the trunk just the other side of the left back seat. and a little close to the tire house.
Sometimes the current sensing resistor in it has a cracked solder joint.

Bali26

Thank you Yamae,

I did open it up but didn't see anything burnt or melted. I will check again for any cracks in solder.

I'm wondering if I can jump wires on the connector coming into "brake light failure sensor" to diagnose it?

Yamae

You are welcome, Bali26.
You can jump wires but it turns on the brake light warning indicator in the dash.
But don't worry because you can disable it removing a resistor but I forgot which one. I will try to find the photo when I did so.

LScowboyLS

guys, you very likely have one or more broken wires inside of the wire bundle inside the curve of the driver's side trunk hinge.

PureDrifter

iTrader: (10)

http://www.lexls.com/tutorials/lighting/bulbout.html

Bali26

Yes its either the harness or the lamp failure box.

I'm leaning more towards lamp failure box because all other lights are fine and car runs fine too.

What method is best to find which wire is broken when there's no visual crack in insulation?


Bonus qn: I opened up the brake pedal switch and it has 2 switches within it (four wires going in). One switch that connects when brake pedal is depressed (for brake lights and gear lever) and one that disconnects at the same time. What is the second one for?

LScowboyLS

never seen a case of this particular trunk hinge wire breakage issue that wasn't obvious via careful visual inspection, in fact, at least one of the wires is typically completely severed into two pieces!

Bali26

Just an update.

It was the lamp failure box. The soder on two of the male prongs had cracked on circuit board.

Re-sodered and working perfect now.

deanshark

Pretty sure the second is for the cruise control shut-off.

Bali26

Ah thanks just couldnt figure it out was driving me nuts.

LScowboyLS

Concur.