Question, Ive been working on my disk brake conversion over the weekend here. I need to know what would cause me not to have brake lights, I have running lights (both sides) and on the pass side I have turn signals, its been this way since I got it. The truck has never had brake lights since Ive gotten it and I hoped that the new brake switch would cure it but it hasnt yet.

 

Assuming then that the new brake light switch is not defective, and given the fact you only have one turn signal, it's a strong possibility that your turn signal switch is bad.

Check for continuity at the brake light switch and then follow the circuit until you find the dead spot.

Are you using a pressure type or mechanical brake light switch?

 

Its the switch that came with the kit which is the same as the original one with the 2 little prongs that the wires plug onto

 

Start with the easy stuff - have you checked to see if you have 12V power between one of the wires on the switch and ground yet?

 

No I figured since I had running lights and the turn signal on the one side I had power running back there to the lights. I will check on that first thing in the morning.

 

Ok lets start with the fundamentals.

You have two filiments on the tail light bulb one is brighter than the other. Likewise each has a wire that feeds it.

The dimmer of the two is the running light and it is connected to your headlight switch. The brighter of the two has a dual purpose - it acts as both brake light and turn signal.

The circuit for the brake light starts with HOT power and goes to the brake light switch (either of the two pins on the switch) Then it flows up to the trun signal switch. With the turn signal switch not actuated, The power flows out the switch into BOTH brake light wires to turn on brake light when you step on the pedal.

If you select one of the turn signals, the opposite one is still powered by the brake light switch power and stays on constantly. The side that is selected, gets power from the flasher (through the turn signal switch) that is powered by another source. Thus the power flowing through the flasher causes it to flash.

So, no brake lights, but the trun signal (which is the brake light as well) on one side works.

Here's what I would do. First, take your tail lights apart and make sure each socket has a good ground. I would almost be tempted to grind a spot on the frame and screw on a redundant ground wire and solder it to the side of the socket!

Try the lights.......Still no workee?

Second, if you have a turn signal switch that is built into your steering column take it out and clean it thoroughly and re grease it. If you have a column clamp on signal switch, Try it .....Still no workee, check that your wiring is the same as in the drawing below, try it again, and if they are ok then replace the column clamp on switch.

Drawing:

 

Ok, I saw your master cylinder post the other day. If you have not replaced that unit and your wheel cylinders and bleed the system, then your not going to have brake lights.

 

Doy!

That's a pretty good point too. I kind of assumed he had hydraulic pressure! If no, your right Marty - no workee at all, the brake light switch is hydraulic pressure activated!

 

Yes new master cylinder is in, the new disks and calipers are on. We were bleeding them when I had my brother check to see if they were working. The only thing not hooked up yet is the vaccum line to the booster.

 

A dumb question; are you running switched power or constant power to the brake light switch? If you are using switched power is the key on when you test the brake lights.
Just a thought.

 

Ummmm, I dunno I never thought about that, I will try it with the key on just to see... lol

 

Brake lights power and running light power should be hot (constant), power to the signal lights should be switched.

So, your headlights, parking lights (front) running lights (back) and brake lights should all work without the key.

You should need the key in and on for the signals to work.

 

Ok I got under the truck and tested to see if I had power when the pedal was down. With the key off there is constant power going to the brake switch but nothing comming out of it and its a new switch that came with the disk brake kit.

 

Well, there you go. Looks like either the new switch is bad or you've still got a bubble of air behind it. You can verify that this is your problem and check the wiring/lights at the same time by pulling both wires off of the switch and shorting them together. The brake lights should come on if everything else is good. I've never been a big fan of the hydraulic switches anyway. I prefer a good mechanical switch that operates off of the pedal. Generic switches of this type are widely available and easy to install.

 

That was it, I bled the rear brakes abit just to see and once I got fluid back to the cylinders the lights came on, Thanks .....