46 Pontiac brake lights stay on,

[Pont 46]

46 Pontiac two door coupe, 6 volt negative ground

 

Brakes lights wont go off, or go on with headlights in off postion.

Changed pressure switch on master cylinder , still stay on.

Pumped brakes a bunch no chane.

When I turn head;ights on, or tailights on via headlight switch brakes lights come on, wont go off. With headlight switch in  off postion, nothing, no brake kights at all 

With headlight in parking lights only postion same result brake lights stay on.

I have tried different lights with same result.

i am using correct light bulb 1154 for 6 volt.

Have tried switching postions of connections at pressure switch with same results. 

 

Any idea, or a something I should try next would appreciate it.

 

 

[DFeeney]

The brake light switch should have 2 wires on it.   If you remove one wire does the brake lights go out.?  it should.  6 volts come to the switch on one wire.   The switch is normally open and closes with hydraulic presser and leaves the switch on the other wire to go to the brake lights.   Get a test light and you can read the system one point at a time.

[m-mman]

A hydraulic brake light circuit is pretty easy.  A fluid pressure activated on the master cylinder and two wire connections. 

ONE wire goes from the switch to the brighter filament on the dual filament bulb.  

ONE wire comes "from the battery" and is hot at all times, just sitting there, waiting for the fluid pressure to make the connect and light up the bulb.  Note: "from the battery" means the it comes from a source that is always hot. A terminal block, a connection at the starter, a source at the fuse box/panel. 

 

Testing:

1. Make sure it is your brake light filaments that are glowing (NOT YOUR TAILLIGHT filaments) A jumper wire to the removed connector at the brake light switch should verify this. Removal of the lens will let you verify that only one filament is glowing and that it is is the correct filament. 

 

2. The other wire should be hot at all times. Use your test light to verify.  IF power going to the switch is not constant or comes on or off with the position of the headlight switch then you have found your problem. 

 

Not a Pontiac expert; Could the brake light power be coming from the headlight switch? (since the headlights are powered from the battery and getting power all the time) It may be the factory source of the power. 

Could the old cloth insulation be broken and headlight power is getting to the brake light because the wires are touching? 

Could a filament be broken and sagging in a bad bulb and making a connection between the headlight (aka tailight) power and sending power back into the brake lights? 

 

Get your test light out and report back 

[Pont 46]

Thank you for all I  will start working on these suggestions.

 

One note, yes the brake pressures wire does connect to the headlight switch.

 

Will recheck wiring diagram

[Bloo]

All good suggestions so far.

 

Is this a new problem? Did you ever see it work correctly or has it always been like this since you've had the car?

 

Does the car have signal lights added, and if so, do they share the 1154 brake/tail light bulbs?

 

 

 

 

 

[Joe Cocuzza]

1 hour ago, Pont 46 said:

Thank you for all I  will start working on these suggestions.

 

One note, yes the brake pressures wire does connect to the headlight switch.

 

Will recheck wiring diagram

Could be a faulty headlight switch or wiring