Brake lights staying on when lights are in ON position

[T4Mike]

I tried to find a thread about this but couldn't really find anyone with the same issue...

When the lights are not turned on, everything is working fine. But once I turn on the lights from the light switch, the brake lights stay lit up as if the brake peddle is pushed. I've replaced every bulb and the brake light switch.

Anyone ever have this problem? I can't pass inspection without working brake lights obviously.

Thank you

P.S. Can I hook up two basic red trailer lights to my rear bumper and run a wire with an inline 15 watt fuse to the wire of the actual brake light switch?

 

[89FourRunner]

Did you ensure the brake light bulbs were double filiment type?

 

[T4Mike]

Yes.

 

[Bad_Vision]

Curios, I would think it would be a crossed wire in the column or at the main fuse block.
Best thing to do would be to test all the pig tails to trace the power to its start point.
This takes time but I don't see a quick fix to this issue.

 

[T4Mike]

Could it be the actual headligh/turn signal switch?

 

[flyinhawaiian01]

If I remember correctly, it is possible to put the dual filament bulbs in backwards, which results in both parking and brake lights to come on at the same time.

Pull both rear parking/brake bulbs out, start with only one (preferrably left so you can see it while you're in the cab). Look at the two tabs on the bulb, one is offset from the base. Align the closest tab to the base of the bulb with the longest slot of the holder. Do not put the bulb back into the housing.

Turn on parking lights, see which filament is lit up. Now, press brake pedal, see if both come on. If good, then do the same on the other side.

If however, you get both brake and parking when only the parking lights are on, you definitely have a short. If you have a trailer module, disconnect it, that may be the cause of the short.

If you don't have a trailer module installed, you'll need to start doing some tracing of wires to find where they are shorted. Start with a test light, disconnect the white molex plug from the rear lamps, test both lamps to make sure they aren't shorted or corroded somewhere that's creating a jump from parking to brake.

You'll have to test from there forward, all the way up to the dash where the brake switch is at, as well as into the turn signal stalk. If its the stalk, luckily they still sell brand new ones, just bought one a year ago.

 

[RAD4Runner]

Could it be the actual headligh/turn signal switch?

I doubt it brake light wiring does not run up to the steering column.

Make sure you are not seeing the rear parking light coming on like flyinhawaiian01 says.

The trailer connector is a common cause of lights issue. Those vampire taps suck like vampires do and they expose stock wires and lead to corrosion.

Gotta start physically tracing wires to be sure.

If I remember correctly, it is possible to put the dual filament bulbs in backwards, which results in both parking and brake lights to come on at the same time.

Pull both rear parking/brake bulbs out, start with only one (preferrably left so you can see it while you're in the cab). Look at the two tabs on the bulb, one is offset from the base. Align the closest tab to the base of the bulb with the longest slot of the holder. Do not put the bulb back into the housing.

Turn on parking lights, see which filament is lit up. Now, press brake pedal, see if both come on. If good, then do the same on the other side.

If however, you get both brake and parking when only the parking lights are on, you definitely have a short. If you have a trailer module, disconnect it, that may be the cause of the short.

If you don't have a trailer module installed, you'll need to start doing some tracing of wires to find where they are shorted. Start with a test light, disconnect the white molex plug from the rear lamps, test both lamps to make sure they aren't shorted or corroded somewhere that's creating a jump from parking to brake.

You'll have to test from there forward, all the way up to the dash where the brake switch is at, as well as into the turn signal stalk. If its the stalk, luckily they still sell brand new ones, just bought one a year ago.

 

[Bad_Vision]

I doubt it brake light wiring does not run up to the steering column.



Make sure you are not seeing the rear parking light coming on like flyinhawaiian01 says.



The trailer connector is a common cause of lights issue. Those vampire taps suck like vampires do and they expose stock wires and lead to corrosion.



Gotta start physically tracing wires to be sure.

Actually RAD it does go up to the steering wheel because your turn signals and parking brake light are controlled there. It also goes into the gauge cluster as it has a out light detector that shows brake when a bulb is out.

 

[theking11863]

Actually RAD it does go up to the steering wheel because your turn signals and parking brake light are controlled there. It also goes into the gauge cluster as it has a out light detector that shows brake when a bulb is out.

Wait, the brake light is supposed to come on in the cluster when a bulb goes out?

And I've had the same thing happen to some LED's I bought. Figured they were just crappy china LED's and condemned them since my old incandescents still work

 

[Bad_Vision]

Lol yes but the problem with LED bulbs is they do not have the correct resistance value so they trip the brake light even if they are working. There was a right up done on how to add a resistor to the brake wire at the light to make them work correctly.

 

[theking11863]

interesting. I need to find this then...

And wtf. My dash never lit up when I had a bulb go out. I only found out after I got pulled over olice:

 

[RAD4Runner]

Actually RAD it does go up to the steering wheel because your turn signals and parking brake light are controlled there. It also goes into the gauge cluster as it has a out light detector that shows brake when a bulb is out.

... My dash never lit up when I had a bulb go out. I only found out after I got pulled over olice:

I guess it depends on what truck-year-model. (I haven't tried this on my first-gen.) That's why I'm adamant that posters should always indicate truck-year-model on their posts. Else, we waste time going back and forth.

Maybe it's just a simple case of shorted wires in the harness leading to the back of the truck.

 

[theking11863]

Maybe it's just a simple case of shorted wires in the harness leading to the back of the truck.

Could be, but to be honest, I don't really care much. In my opinion, that's something that should be checked periodically anyway :shrug:

 

[T4Mike]

Ok...

This is issue started while driving one day. It didn't happen after I replaced any bulbs. I replaced every bulb and added aftermarket clear lenses and headlights as an add on a year or so ago. But since this had happened, I did check the bulbs. I Will check them again if it's necessary for this thread to continue.

I'll also add...
About a year ago I found hidden trailer hook up system/wires installed on the right rear tail light. Before I found this, and the reason I found it, a fuse kept blowing. Long story short, there was water in that back storage cubby hole that kept splashing against the trailer wires and shortening out he fuse. I removed all the trailer wiring and excess. So, that was a year or so ago and shouldn't be a part of this issue. I'm only listing it for past history for if maybe someone has a stroke of luck that they know an underlying issue that could have stemmed from this.

About 8 months ago, I'm driving and my mother is behind me and she calls me to tell me all of a sudden, my brake lights won't go out. So, this issue is not from incorrect bulb installation. One mechanic said he thinks it's the headlight switch since that's the only time the brake lights stay on is when the lights are in the ON position.

So... I Will go recheck all the bulbs if it Will help this thread. But I've done this already in the past. My lights have been like this for about 6 months now. I'm disabled with back issues and never drive at night anyways, so I never cared to pay much attention to it.

The only thing i can guess is maybe a wire short being that it's 30 years old... Or the headlight switch.

Also... Can I install two basic red trailer lights to my rear bumper (Which Will be the ground of course), and run a 15 watt inline fuse directly to the brake light switch itself? That way when the brake pedal is pressed, it'll automatically turn on these lights as working brake lights to pass inspection.

 

[flyinhawaiian01]

I guess that would depend on whether your inspection allows external lights as a replacement to OEM brake lamps/housing.

Now that we know it wasn't due to an incorrect bulb installation, that this happened while you were driving, we can rule out most of that stuff I posted to check, but you will need to do some basic testing here.

I'd start at the brake switch mounted at the brake pedal. There should be 2 wires at the pedal. unplug molex connector from switch, use multimeter on 12v dc, connect black to ground somewhere on vehicle, use red to check each wire in the molex connector.

You should have only one with 12 volts, turn parking lights on and check again, you should not see any difference. If you do, there has to be a short between the two circuits. From the schematic I'm looking at, they are completely separate circuits, and for them to interact like that, it has to be a short or bad ground between the two.

The wiring colors I see in the schematic are:

green/red at the switch, that wire should be supplying +12 from the fuseblock to the switch.

green/white at the switch, that wire should run directly to the stop lamps +12 input. If you have cruise control, there is a tap off of this wire that runs to the CC module. Also, there is a tap (looks like the same spot in the harness) that goes to the efi ECU. Not sure why the ecu looks at the brake lamp function, this could possibly be for the brake light in the dash if that wire sees more resistance when a bulb burns out?

White/black at the lamp, should be grounded. Check to make sure this is grounded all the time, also check if it is when parking is on as well as off.

That there is the complete circuit for stop lamps, from fuse to ground! The schematic I'm using is an '88 4 runner manual. If you have a newer 4r, it may be completely different.

Now, you could bypass everything completely by just cutting the green/white wire at the switch, and then running a new wire (at least 14AWG!) directly to your rear lamps. Cut the green/white wire at the bulb housing and connect your new wire. This will effectively bypass the stock harness, and you don't even need to bother with buying/mounting/wiring in new external lamps!

I'd also re-ground the stop light's white/black wire at the lamp directly to the frame at this point. Hell, I'd probably do that first before running a new wire from the switch!

Try this first, let's see where it goes.