No brake lights :(

[ChalkOutline]

I have "new" tail-lights and bulbs, but no brake lights. I didn't have any before I swaped the lights so nothings changed (I had hoped it was bad bulbs).
Is there a switch like most civilian vehicles, or is it pressure operated, or.....

Obviously with this question comes the follow-ups:

1. Where is the switch?
2. How do I check/test it?
3. How can I fix it?
4. If all else fails and I need to replace, anyone want to part with a working model?

Thanks Guys,
Jeff

[rpgdeity]

There is a pressure switch that turns on the brake lights. It is located on the inside of the drivers side frame rail approximately directly underneath the master cylinder. If you follow the brake lines from the master cylinder down to the frame rail, the line goes into a big junction block, and the switch should be there. I would check to make sure it is plugged in properly and that the two wires coming off of it are connected. Next would be to use an ohm or voltmeter and see if it is turning off/on. There was some talk about a replacement one, I'd have to search past threads.

[ChalkOutline]

Thanks, I found it!! It is plugged in.
I ass-u-me it works by an increase in line pressure when the brakes are applied.
If it is not turning on/off with pedal application, but the brakes are working, does that mean a bad switch, not enough pressure increase to trip it, bad wiring, or ......?
I did a search but didn't find the answers I was looking for.
Thanks Again,
Jeff

[george walker]

yea it pressure operated if the brakes work and you have power going in on one wire but not on the other wire w/ brakes applied then the switch is bad . i think its a standard switch for most all older mil vehs so any surplus supplier should have one, if you have power through the switch then just follow the wires to the back checking along the way to find the break.

[randyscycle]

If you want to check the switch, first verify as George said, that you have power to at least one wire of the switch. Do this with a test light.

If you do, and the power does not go through the switch when the brakes are applied, then you have a malfunctioning switch, or a plugged fluid passage in the brass block it screws into.

I have had some luck removing the switches in the past and using a little contact cleaner to clean out the fluid port and then blowing them gently out with low pressure compressed air. Being that the switch is in such a low spot, it tends to accumulate the goop that brake fluid turns to after 40 years.

[LuckyPabst]

Make sure the 3-lever switch is not "off" or you won't have brake lights ever. I forget the position names, but I think "drive" is where you want to be.

Chris

[randyscycle]

Make sure the 3-lever switch is not "off" or you won't have brake lights ever. I forget the position names, but I think "drive" is where you want to be.

Chris

Oh yeah, then there's that.......Thx Lucky......

[Barrman]

The top lever on the 3 lever switch needs to be in one of the two postions to the right of center. That is the only way power will go out for your blinkers and brake lights.

This page shows you where all the wires in the lighting system go. I think wire 75A is the power for the switch, but I haven't messed with mine in about a year and have a 50/50 chance of being wrong.

http://www.m715zone.com/vb/pages/man...g/lighting.pdf

[wrecker]

If you need a switch, I have an extra. The one from a Harley Davidson of some year is similar and available new. I think FNG went that route. Another option is to mount a pedal activated switch from another vehicle. Not at all difficult. My wires have been extensively modified by more than one PO so the diagram didn't always work for me.

[george walker]

additionaly when the light switch is off, not only the brake an t/s lights are off but so is the horn