Brake (Stop) Lights will not come on

[mrgerke81]

I noticed yesterday my brake lights not working correctly. I checked bulbs and they are ok. I noticed that if you hold down brake pedal for about 2-3 minutes they sometimes will come on either full strength or dim then go full strength. I checked wires that go to master cylinder. When you put a volt meter on the ends of wires after disconnecting I get 24 volts. I checked continuity of switch on master cylinder and it is open until brake pedal is pushed then it closes giving 0 resistence. Is there another switch or contact somewhere else to check? I was wondering where the two wires that come off of master cylinder go to. Is there some sort of relay or something. I didnt understand why you have a 24 volt power wire then a ground. What does the switch do in the master cylinder, just ground it out or what?

Thanks

 

[emmado22]

I'll bet that you have a bad brake light switch on your airpack. If it is the old style switch, it will be on the end of the airpack. Now is the right time to change with with the newer, much safer air operated air switch. Saturn Surplus has them for under $30. see below for more info

http://www.steelsoldiers.com/index....ht_switch&name=gallery&include=view_photo.php


Do a search, this topic has been addressed several times here..

What wires are you referring to on your master cylinder?? I've never seen a deuce with wires going to the MC.

 

[mrgerke81]

I am sorry I ment to say the wires are coming off of the air pack. When I screw out this switch, am I going to have to bleed the brakes when I reinstall a new one?

 

[Blacksmoke]

If you have the air operated switch, you won't lose any fluid. I also did this upgrade but mine quit working too. And when they did work, they didn't come on unless you were really braking hard. I'm tired of messing with it, so I'm installing a microswitch operated off of the brake pedal.

 

[mrgerke81]

And another question the two wires hooked to the old style switch. One wire is hot with 24 volts and the other seems to be a ground. Or at least the wire that doesnt have any voltage on it causes an arc when you pull the harness off and short the terminals together. Is the wire with no current supposed to be a ground or is it shorted out somewhere else in the truck causing my problems.

 

[oifvet]

Add me to the list of "been there, bad switch" deuce owners.

Easy fix, though.

 

[Jake0147]

And another question the two wires hooked to the old style switch. One wire is hot with 24 volts and the other seems to be a ground. Or at least the wire that doesnt have any voltage on it causes an arc when you pull the harness off and short the terminals together. Is the wire with no current supposed to be a ground or is it shorted out somewhere else in the truck causing my problems.

It'll show ground with a test light or DVOM, but you're getting this reading through the tail lights. A light bulb is essentially just a signifigantly undersized wire.

 

[Floridianson]

It'll show ground with a test light or DVOM, but you're getting this reading through the tail lights. A light bulb is essentially just a significantly undersized wire.[/quote]
With that being said if you were going to check the circuit then you would remove the two bulbs and then check the circuit and it should be open.
When you completed the circuit did the lights come on?
It's always good to bleed the system when it is opened starting with the air pack then the wheels.

 

[Flatlander]

What has worked for me is to pull off the switch, spray some lubricant in the switch, and replace it.

Works on mine, anyway....

 

[Blacksmoke]

Heading to a show this weekend so I am currently installing a microswitch that will be hooked to the master cylinder rod with a spring. It's kind of an unhandy place to mount a switch but I found a great place to put it. The microswitch will contact as soon as I hit the pedal & the spring can just stretch for the rest of the travel.

 

[98hd]

The circuit also goes through the turn signal lever.

You can check it there (do a search on here for wiring cad drawings).

When you press the brake lights the brake light wire should give you power.

It then goes through the switch and out to each taillight wire.

 

[dabtl]

The simple solution may be GROUNDS. Bjorn made a believer of me. I replaced every star washer on the lights from front to rear with internal/external star washers from Grainger. I cleaned the surfaces and replaced every rusty bolt. Front to rear on the lights. They work fine now. I replaced the brake light switch, old style, in the process as it was making a completed circuit without the brakes being applied. I put on the conversion kit in just a few minutes. You have to change the plug out also.