I am pretty sure that is accurate for a ride from the 1950s. And Stu's statement is a bit inaccurate.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.
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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