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On my 1965 F100 the rear brake lights come on when the key is engaged and stay on always. They do not flash. The front directionals come on without flashing when the blinker is engaged in that direction. I have replaced the flasher switch and grounded each light and replaced the bulbs. I bought a new pressurized brake light switch but the master brake cylinder is a newer replacement and has no port for the switch. The photos below show two odd devices along the wiring, one just behind the left headlight under the hood and the other under the dash. Both have the wires from the directionals running into them. I've written to Littelfuse asking what the metal box under the hood is. No idea what the black plastic thingee under the dash is.
Any ideas on how to get it all functioning properly?
LITTLEFUSE is the relay for the horn(s). Sort of an automated switch.
C4AZ-13853-A - RELAY and BRACKET ASSY. HORN - #C4AB-13853-A
The other one under dash looks like something that came apart and they left the remnant plugged in. Might be the emergency flasher switch. The below part but only the black base where it plugs in possibly. Otherwise, I'd need more context of where in the harness that is.
If your master cylinder doesn't have a brake light connector, you'll have to get some sort of aftermarket brake light switch to put under/over your brake pedal. The brake lights may be constant on because the switch is a normally closed switch. I'm not sure off hand. Pretty much means it only turns the brake lights off when the it's actuated. Or you could get a new master cylinder with a switch on it.
I had a similar problem with the acting weird staying solid sometimes. Turned out to be corroded bulb receptacles that were shorting the 2 bulb contacts together. I cleaned them up real well and they started functioning correctly. You can diagnose most of this with a test light.
