1966 Brake Light Switch & Rough Idle Issues

Hello Bill,
I just came across your blog, and first off, I wanted to say thank you for all the valuable information that you provide to Lincoln enthusiasts; just after reading a couple of posts and your responses it gave me a better understanding of what I’m looking for. My issue is this:
I have a 1966 Lincoln continental that I have owned for a couple years, the car is not a daily driver, just a weekend cruiser or special occasion vehicle. The car runs pretty good, other than a rough idle, and delay in throttle response if I’m at a traffic light.
The problem that I’m trying to currently fix I believe is the brake light switch, what happens is the brake light (driver side) stays on constantly! I’ve had to disconnect my battery every time I get out of the car to ensure that I won’t drain my battery. I’m wondering is that the brake light switch? And if so would all I need to do is replace it, I was told that it’s underneath the brake pedal or near the passenger side firewall? I have a shop manual but haven’t had much time to look through it (original shop manual).
That’s my main issue; other than that the car runs well, any advice about the brake light switch and the rough idle would be deeply appreciated.
Thanks again for the blog –
Nima
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Greetings Nima,
We are happy that you are enjoying the blog. The first concern with a rough idle condition should be all of the basic tune up items and their adjustments. These will be spark plugs, high tension wires, ignition points and condenser etc. Next will be fuel and carburetion conditions. If any of these has been ignored for a long period of time the engine idle can be adversely affected. If all of the above are o/k the basic engine condition will need to be evaluated. This includes compression readings and valve condition, etc.
If the brake lights are remaining “on” with your foot off of the pedal the brake switch or its linkage could be suspect. The brake switch however operates the left and right side at the same time therefore I am concerned when you say that only the one side is sticking on. If this is so and your right side is not operating it suggests to me that your turn signal switch may also be faulty. The power from the brake light switch runs through the t/s sw. before going out to the brake lights. The wiring diagram in your manual should guide you further as you test the continuity of the circuit. If we can help you further with any advice or parts please do not hesitate to contact us at any time.
Sincerely,
Bill