- Jun 30, 2004
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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?
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?
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