Brake lights stuck on

[blknblu69v]

Why are my brake lights staying on even when the vehicle is off? This just started out of the blue. Years ago, I installed a vacuum boost and front disc brakes. No issues until recently.
Reading past threads talked about the brake light connector on the brake pedal. I found it under the dash. I took a couple pics with my phone to zoom in and get a better look but nothing stands out to be the issue.
Is it possible there is some corrosion in the switch keeping the connection in place and some electrical contact spray may take care of it?
Or do you think I need to replace it?

 

[chuckji]

Simple check might be to lift up on the brake pedal to see if the lamps turn off.

 

[m_m70]

mine did this and it turned out the switch went bad. simple, cheap fix (hopefully).
unplug the switch or disconnect battery to save lights until fixed.

 

[blknblu69v]

I have to agree. I did try to pull the pedal - no change
I spayed it with contact cleaner - let dry - no change.
I'll get a switch coming and start my stretches to get limbered up for the contortionist positions I'll need to get into to get my body under the dash working on the top of the pedal!
I unhooked the battery and will get the new switch ordered tonight.

 

[admin]

Try first unplugging the brake light switch at the pedal. (don't remove the switch, just unplug the wiring to it) If the lights go out then the switch is the culprit. If they don't go out then you have a short/crossed wires somewhere else.

 

[Steve83]

I agree - figure out the cause before buying any parts.

(click this text)


All vehicles' brake lights work with the key out.

(click this text)

 

[blknblu69v]

Hooked the battery back up, lights stayed on. Unplugged one wire from the plug, lights went out. Removed the switch and did an ohms test. Switch is closed. Ordered new switch. Hopefully get it tomorrow and install it.

 

[jerry]

Hooked the battery back up, lights stayed on. Unplugged one wire from the plug, lights went out. Removed the switch and did an ohms test. Switch is closed. Ordered new switch. Hopefully get it tomorrow and install it.

This seems to be a pretty common problem. Mine decided to get stuck on the way to work, when I went out to go home I had a dead battery. LOL

Replacing it isn't too bad, but does require some contortionist moves!

 

[chrlsful]

the joys of auto ownership...

 

[blknblu69v]

Thanks everyone! I got the part and it took about 15 minutes to get my body into the right position to install it. Hooked up the battery and no lights! Everything is working as it should. Did some other small touch up stuff and took the wife to dinner in it. Sure is fun to see the smiles on peoples faces when they see us go by!
There is always something to work on with 50+ year old vehicles!

 

[bmc69]

This seems to be a pretty common problem.

Yep..I've had to replace quite a few of those. Always considered it something of an odd design...one they abandoned in favor if simple plunger style switches later.

 

[70 sport WA]

I can't believe anyone hasn't mentioned this one, a $0.01 fix.

As I recall, when contact from the petal mechanism and brake switch is broken, that turns on the brake lights. In resting position, contact is made. Sometimes there's a very small gap in that connection even in resting position.

How it develops, I don't know. But I've had a 75 F250 and also on an EB that the brake lights got stuck on. So I taped a penny to the plate and it was enough to push the brake switch plunger and turn off the lights.

Some may find this not ideal, but it's a quick fix. Especially when the brake switch is otherwise working or a new brake switch is going to result in the same small gap.

 

[Steve83]

As I recall, when contact from the petal mechanism and brake switch is broken, that turns on the brake lights.

No, that's wrong. Lights come on when the circuit is CLOSED (contact MADE) and go off when it's open (contact broken). The BOO spring normally holds the switch contacts apart. When the pedal is depressed, the pushrod eye (which is slightly oversize to the pedal arm pin) pushes one of the contacts against the spring until it touches the other contact, turning the lights on. Then the eye hits the other side of the pin & stops pressing the switch farther, even if the pedal continues down. It's a very logical design because it relies on FORCE on the pedal to activate the lights, instead of POSITION (like the newer pin switches do). That's why newer switches are called BPP (Brake Pedal Position) instead of BOO (Brake On Off).

 

[70 sport WA]

I don't know, it's been a while...I just remember on my 75 F250 noticed the brake lights were on at work and the penny + tape corrected it. Perhaps I need to look more closely at the mechanism on the Bronco. Am I imagining it happened? Maybe, lol. But when the brake lights stay on when you walk away from the truck (nothing depressing the pedal) and drain the battery, there's a reason if the switch is still good. That penny closed the gap and stopped it from happening.

Come to think of it, in a 93 Honda Civic I had, a small plastic stopper dried up, cracked, and came off in the brake petal area (looked like the tip of a crayon). Penny worked there, too.

Correction: You are absolutely right, Steve, I got it wrong....just looked at the mechanisms for the 75 F250 and an EB. Totally different. Poor assumption on my part that they were similar.