Brake Light Issues '64

[juiced99ws6]

So I drove my 1964 Thunderbird home about 400 miles and was under the impression from a friend that before I left on my trip home all my lights worked fine. First day I drove it to work after that I was informed my brake lights didn't work. When I got home I took a look and realized that they are just stuck on all the time.

If key is turned to the run position my brake lights come on and will not go off. I unplugged the pressure switch from the master cylinder and they stayed on. I then jumpered the wiring since I did on know if the switch was normally opened, or closed. Lights stayed on. If I turn on my signal the lights will blink between dim and bright like they should if brakes were applied and the turn signal was on.

If key is off and I turn the headlights on, all the lights work and the taillights are dim. as soon as I turn the key back on then the taillights light up bright again.

I really do not know where to go from here so any help is appreciated.

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[bwssr]

On the front of your master cylinder there is a switch. It operated by the brake hydraulics when you step on the brakes. It could be stuck on. Unplug it and see if your brake lights go out.

 

[juiced99ws6]

I have unplugged it and no change. I also jumoered the wires in case it needed to be closed to shut the lights off and no change.

 

[bwssr]

Then there must be a relay in your trunk that is stuck on. I had a 64 for a while but it has been some time. I know 65 has a relay in the trunk behind the back seat.

 

[juiced99ws6]

That was my assumption as well. I could not find the relay, can you point me in the right direction?

 

[bwssr]

Try http://www.**************/ or http://www.tbirdhq.com/ or http://www.larrystbird.com/1958-1966-ford-thunderbird-products/

 

[juiced99ws6]

Thank you so much, I had meant that i haven't been able to find it in the car though. I looked in the trunk at the forward part and can't see anything back there.

 

[Hantz101]

Check behind the washer fluid bag. Driver's side fender wall

 

[juiced99ws6]

Thanks! That is where it was. I never did findthe exact problem but i ended up running new wires all together. I had replaced the relay and the switch with no change.

 

[Hantz101]

So what exactly did you do? I think I have it narrowed down to the stop light switch or the relay, but not sure how to check either one. Where did you run your wires?

 

[juiced99ws6]

Mine were stuck on. My relay plug had 2 hot wires as soon as ignition was turned on and 2 solid grounds at all times. After ensuring my brake light switch worked on the master cylinder I just clipped one of the grounds and spliced a longer wire and ran it to the brake light switch. I cut both wires off that switch and ran the new wire to it and another coming off to provide ground. Now the relay can only get a ground a ground when switch is activated. I don't know why mine wasn't working like that in the first place but now it functions fine.

 

[Hantz101]

Ok, but how did you check your brake light switch? I still dont understand how a fluid pressure can create an electrical current

 

[juiced99ws6]

The pole in the switch is throw by brake pressure rather than a push button or toggle switch. You check it using a multimeter and place a lead on each switch contact and have someone step on the brake to see if your resistance changes from OL to a resistance number. Normally about .1 ohms. If your lights are stuck on you can also just unplug the switch to see if they go out or stay on.