Brake lights...is there a pedal switch??

[m37_power]

Are the brake lights attached to a switch on the pedal or something else? Mine arent working and im trying to trace things out to see whats going on. Just checking to see if there is a switch on the pedal or not.

[MSeriesRebuild]

Are the brake lights attached to a switch on the pedal or something else? Mine arent working and im trying to trace things out to see whats going on. Just checking to see if there is a switch on the pedal or not.

A pressure switch was used, early trucks, it was mounted in a brass block inside the left frame rail along with the lines that split going to the front and rear axles. Later trucks, it was in a port at the top rear of the master cylinder casting. Most often we see it in the master cylinder, many early trucks were changed to this configuration along the way. Early master cylinders did not have the threaded port, of course most were replaced with cylinders of the later design before leaving military service.

Just so you know, the brake lights are wired through the main light switch. If your truck has no turn signal system, brake lights are on an individual circuit. If it is equipped with turn signals, brake lights are incorporated in with them. Many folks not familiar with military wiring are also not aware that the main light switch must be turned on to either the brake light position or the service drive position before the brake light circuit is energized. This information applies if the light switch and wiring are the military standard system, if your truck has had its wiring altered or the original military light switch has been replaced with some other type component as many have after getting into civilian hands, there is no telling what you may find in your rundown.

[m37_power]

That helps alot. From what i can tell, the factory harness hasnt been touched. I didnt know that the switch had to be in one position or the other for the brake lights to work.

[MSeriesRebuild]

That helps alot. From what i can tell, the factory harness hasnt been touched. I didnt know that the switch had to be in one position or the other for the brake lights to work.

Be sure to turn to the proper switch selection and try it first, you may find that it works ok.

[m37_power]

yep, im still have alot to learn about my m37 thats for sure. Im going to try them tonight with the switch turned to the 2 postions that it needs to be in.

[Lifer]

For those of you who don't (yet) own a military vehicle and have always wondered why everyone has their lights on in a convoy, there's the reason. No headlights = no brake lights. Very handy in time of war under blackout conditions. Not desirable on the Interstate! For those of you who do have an MV but do not habitually turn your lights on when you start out in the daytime, please get in the habit. It will make following you much less stressful!

[MSeriesRebuild]

For those of you who don't (yet) own a military vehicle and have always wondered why everyone has their lights on in a convoy, there's the reason. No headlights = no brake lights. Very handy in time of war under blackout conditions. Not desirable on the Interstate! For those of you who do have an MV but do not habitually turn your lights on when you start out in the daytime, please get in the habit. It will make following you much less stressful!

Not quite right, it isn't necessary to have the head lights on to activate brake lights and turn signals. The first position is brake lights only, (embossed right on the switch housing), if you have turn signals, they too are activated at the same position. In this position, no lights are on until you apply brakes or use turn signals. Headlights are not energized until you move the top lever to the next position, (embossed service drive).

Standard practice is "lights on for safety" during convoying, but it is not necessary to have headlights in order to get brake lights or turn signals.

My habit is this, never turn the top lever to the off position, mine stays in the stop light position all the time except when I need headlights. This way, I don't take off not thinking and without brake lights operational.

[Lifer]

My bad! Thanks for clearing that up Charles. When I was driving them while on active duty, we never used the "first click," It was either lights on or blackout...mosty "lights on." Guess I assumed wrong, there, and we ALL know what that stands for.