57 Tbird question

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action
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Re: 57 Tbird question

Post by action »

Steve K wrote:That should not be the case. The brake lights should work even with the engine off. The fact that it works when running suggests to me a bad switch on the master cylinder. When the engine is running, you get enough vacuum assist to activate the switch. When it's not running, you don't. Imagine the scenario where you are driving along in traffic and the engine stalls. Your brake lights now fail and you get rear ended. No way it would have been engineered that way. Swap out that inexpensive switch and avoid disaster.
I am pretty sure that is accurate for a ride from the 1950s. And Stu's statement is a bit inaccurate.

The brake light circuit works based on the ignition key being in the on position. (not the engine) The brake lights and all other running lights were connected to a switched side of the fuse box. Later vehicles had the brake light system connected to an always hot or un-switched side of the fuse box.

In the hypothetical scenario above the brake light circuit would still be powered up.
The engine running or the engine stalled out is not the controlling factor. It is the ignition key switch position that is the controlling factor.
So the engine stalls out and the ignition key is in the ON or Run position, there will be power to the brake light circuit. The engine just won't be running.

Again, I a pretty sure this was changed at least by the early to mid 1960s so the brake light circuit had power even with the key off.

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Re: 57 Tbird question

Post by Mike »

Before changing the switch use the check light you have and see if it's getting power or not with the ignition off. You don't want to waste money paying your mechanic to change the switch if it's wired to work that way.
First check the test light by touching the clip to the negative battery post and the pointy end to positive to make sure the light works. Then pull the plug off the brake light switch, clip the wire of the test light to bare metal and stick the other end in either side of the plug and one side should make it light up. If nothing happens try again with the ignition on.
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Steve K
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Re: 57 Tbird question

Post by Steve K »

I think we're all saying the same thing IF the difference in the scenario is the actual engine running vs. just having the ignition switch on. I agree testing with a meter or test light is a good idea. But if in fact the actual engine has to be running for the brake lights to work then it is possible there is just not enough pressure on the brake light switch to trigger the brake lights and the engine running provides the vacuum for the booster to activate them.

I had a 56 Ford Victoria back in the day and I swear those brake lights came on when the pedal was depressed even with the ignition switched off which is how I think they are intended to work even in the mid 50s. No matter the cause, if it works only when the engine running it is not "fixed". Look a bit further.
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Re: 57 Tbird question

Post by TonyC »

Actually, that could make sense if it turns out to be actually the case consistently. I know that we Ford-fanatics are used to almost everything being energized with the key in the "ACC" position...but what if that was not the case in the '50s, when all the creature-comforts we are now used to were just being marketed? Suppose that, in the '50s before Ford went in a different direction, they followed a practice of having all the electrical stuff energized only with the key in the "ON" position, and very few items energized in the "ACC" position...like, say, GM has done for decades? And suppose the brake lights of the mid-'50s were wired to act in such a way, only with the key in the "ON" position, before they decided to change that? I know there are a lot of construction standards that were normal in the '50s which were subsequently discarded by the early-'60s...and '60s standards that were ditched by the early-'70s, and so on.

Sounds logical if Stu's discovery remains consistent with every test. If it does, then that means there was no problem to begin with. Although that sort of thing is just not acceptable by today's standards, it was okay by 1957's standards. Now, if there could be a way to change that, I would advise it, like I altered the parking-light operation to Frankenstein to '70s-and-up standards.

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Re: 57 Tbird question

Post by George W »

Stu, I checked with my local buddy who has a 57 TBird today. His brake lights work without the key on or the engine running. The brake light switch is in the engine compartment down on the brake lines just below the steering column. It's a simple on/off type switch that simply screws into a brake line block and connects with two push on wire terminals. If you have power brakes it may be necessary to press the brake pedal extra hard to light the brake lights with the engine off. If your brake lights in fact, do only work with the key on and the engine running, then I would expect the feed wire to the brake switch to be connected to the wrong circuit.
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