Brake Light switch

P

Porsche

Junior Member
I have a 1939 Ford and the brake lights are not working.
Took it for it's first ride this year and when I returned I noticed that the brake lights were on and would not turn off.
Crawled under the car and found one of the wires to the switch was off.
Reattached the wire and the lights went out. How does that switch work?
It seems odd that the lights light up when the circuit is broken.
Can someone explain this for me.
I have a new switch to install but just want to understand this.
 
Is it a pressure switch. I had hydraulic brakes on my first Model A back in 1968. Never did trust it and went with a mechanical switch.
 
Tacoma Bob said:
Is it a pressure switch. I had hydraulic brakes on my first Model A back in 1968. Never did trust it and went with a mechanical switch.
Click to expand...

Maybe there would be more eggspertice on the later Ford forum, but whether it is a mechanical switch or a pressure switch, an open circuit is still an open circuit, and the lights should not light when the circuit is broken. I looked at a diagram of a '40 Ford and it has a series wired switch, so when its open its open. So, the circumstances seem confusing. You would have to have a relay in the circuit to have it have the opposite results, and it would not make sense to have a relay in the brake light circuit.
 
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