Finer Points of Adjusting a Brake-Light/Stop-Lamp Switch

BonzaiDuck

Lifer
Jun 30, 2004
15,699
1,448
126
No Master Mechanic I. I learn what I need to learn, to achieve full readiness and vehicle reliability for the fam-damn-ily. Everything must be tip-top. The question I pose results from the very prolix discussion of my activity this week repairing the stop-lamp switch or brake-light operation on my brother's Nissan truck.

People who follow the new-car strategy every six years won't likely encounter this problem before they buy a new vehicle, but our family follows the used-car strategy, saving $60,000 on vehicle-asset purchases and $14,000 in insurance premiums over 18 years or three purchase cycles.

This week, I learned about stop-lamp switches. My brother's Nissan 95 hardbody truck suddenly had the brake lights on all the time. I think I caught this failure within an hour or so of its development. Brake lights operate even with the ignition switch turned off. Those rear tail-light lenses were hot -- or close to it. I figured that once I'd extricated myself from this pickle of a pickup-truck driving hazard, I'd replace the #1157 bulbs for the rear stop lights and tail lights. No telling how much wear on the original bulbs had occurred over the time the lights stayed on in the garage..

The general information available on the web suggests that a mid-90s Nissan may show the "ABS" warning light on the dash instrument cluster as well. It suggests that the brake-light/stop-lamp switch may have gone bad. Such a switch looks like these:

Images of brake-light/stop-lamp switches

Notice the black and white sketch on the second row, middle of the page. This shows where the stop-light switch can be found on many vehicles, on the short side of the brake-lever and above its fulcrum. How it operates seems counterintuitive, until you account for this fact. The brake pedal has a return spring with tension to return the pedal to its unengaged position when the foot is removed. The stop-lamp switch is engaged or pushed in when no pressure is applied to the pedal. Pushing down on the brake pedal releases the little black button at the switch's end to a point where the brake-light circuit is closed, turning the stop-lamps on in the rear-taillight lenses.

But don't be too hasty ordering the replacement switch until you've adequately tested the old one. It's a cheap part, and I have a tendency to place orders too soon before investigating causes and effects sufficiently. You test the old switch by connecting it after removing it from its threaded mount. reconnect the negative battery cable; the rear stop-lights should be on. Push in the little black button, and if the stop-lamps are no longer lit up, the switch is still good.

So what caused my problem if my old switch still functions? The top of the brake lever rests against a backplate which has a small hole, and the stop-lamp switch-button would uselessly penetrate that hole if there wasn't something there to stop it. Apparently, manufacturers think it's a good idea to put a small rubber button in that hole, and the stop-lamp switch's button presses against this rubber piece at all times:

Stop-Lamp switch rubber bumper

Pressing the brake pedal releases the switch, as I said, to a point that closes the brake-light circuit. And these little rubber buttons eventually wear out. Advisories tell you to look on your floor-board for any pieces of the old button, and you can skip testing the original brake switch.

So my question? The brake pedal has free travel when you put your foot on it to a point where you can feel the brakes begin to engage. You are supposed to adjust the brake switch in its threaded mount to a specified clearance, but trying to be a midget-contortionist fiddling under the dashboard makes it seem nigh impossible to measure the clearance. So, should the brake-light switch be adjusted to turn the brake-lamp on at the point where you just feel the brakes engage? Or should it be adjusted as a hair-trigger, so all you need to do is just touch that brake pedal to witness the lights go on? Or should it be somewhere in between?
 
Last edited:

mindless1

Diamond Member
Aug 11, 2001
8,031
1,440
126
Somewhere in between. It is useful to be able to put your foot lightly on the brake pedal to signal to others that you are slowing down because traffic ahead is slowing down or you're coast-decelerating up to a stop sign or whatever, without having to actually engage your brakes to do so which gives the driver behind you even less time to react, especially in a high speed highway scenario, even more so if it's rainy or foggy then the drivers behind don't have to rely only on perceived distance changes.
 

Paperdoc

Platinum Member
Aug 17, 2006
2,285
265
126
Agreed. Also, IF this applies to your vehicle, the same switch may be used by the CRUISE CONTROL system to de-activate it when the brake pedal is pushed. So for that reason also it should be somewhat sensitive, but not overly so.
 

BonzaiDuck

Lifer
Jun 30, 2004
15,699
1,448
126
Agreed. Also, IF this applies to your vehicle, the same switch may be used by the CRUISE CONTROL system to de-activate it when the brake pedal is pushed. So for that reason also it should be somewhat sensitive, but not overly so.
It may vary by make, year and model, but Bro's Nissan Hardbody has a separate cruise-control switch, adjacent to the brake-lamp switch.

Looking at the response from you and that from Mindless1, I suppose I incline to the "hair-trigger" side of the debate. I wouldn't be paying attention to this if it weren't for the malfunction described for the pickup.

I hadn't really paid attention to it before, but I checked out the switch adjustment for my 95 Trooper. It's like the trigger on Paladin's (Richard Boone) "Buntline Special" in "Have Gun Will Travel". You just touch the pedal, and the brake lights go on.

These are definitely things you discover in DIY maintenance for old cars. I suppose some people would be in a panic about it. Or they would merely discover their battery was depleted the following morning, unable to start the car. Maybe they'd call a tow truck and have a repair shop recharge the battery. Would the repair shop then take note of the brake light problem? I can't say.

All this trouble for a little piece of rubber grown petrified and brittle with age. Some people suggest securing a penny over the hole fitting with two-sided tape. An Australian fellow offers a YouTube video in which he deploys little square stick-on furniture floor protectors.

It inspires confidence, though, when you prove again to yourself that "Anything can be fixed", as my now-retired mechanic once proclaimed. This was HIS truck. He was good at taking a deteriorated light-bulb fitting for a tail-light and making it work. But to the unsuspecting -- like me -- trying to put in a new bulb totally destroyed his previous work. I discovered that an Isuzu bulb-holder would fit in the tail-light assembly of the Nissan hardbody, locking together the proper way. There IS an advantage for hoarding old, spare parts.
 

BonzaiDuck

Lifer
Jun 30, 2004
15,699
1,448
126
A HELPFUL UPDATE CONCERNING THE RUBBER BUTTON BEHIND THE BRAKE-LAMP SWITCH

You can find someone selling OEM parts to replace the rubber button, but not always. Further, the OEM parts can cost you $15 to $20 -- for single button. The part may even vary between years and models of the same make.

While waiting for an OEM button to arrive in the mail, I was down at the O'Reilly's and Autozone to pick up some tail-light bulbs, and happened to mention my story about the rubber button. The O'Reilly's employee quickly mentioned "We have those!"

What he showed me was the "Dorman" generic product. I thought I would try it anyway, because it cost about $6.

It fits in the hole of the brake-lamp-switch back-stop, but loosely. It doesn't snap into place. What you need to do with these is find yourself a metal washer that makes an interference fit with the small side of the button and lock it in place from the back.

The washer is not going to hurt or cause wear on the button part. It just serves to secure it in place. After that, you could put a dab of Pit-Crew Adhesive on the back side -- with or without the washer, and that will keep that button locked in place with a certain assuring permanence.

Don't rigidly assume that you need to exact same OEM part to fix this brake-lamp-switch problem. Some people use a penny with adhesive; others have found little square furniture "floor protectors" to do the job.