Brake light switch

Steven, here is my 308GTB drysump euro "77 it has two red wires one coming from fuse 1 and the other red wire is going to the brake lights see picture. Rob Image Unavailable, Please Login

 

89 328 has 3 wires - one supplies battery voltage from fuse 23, one goes to the right brake light, and the 3rd goes to the ABS ECU. All previous years should have 2 wires.

Please always state what year/model your car is when asking questions, to make it easier to help.

 

If the switch has only one terminal could it be that it switches to earth through the switch body (I.e switch is now dead). The wiring diagram should show this If a voltmeter shows 12v at the switch (ignition on) but removing the bulb then shows 0 v, this would be a clue. If it’s wired via a relay this won’t apply. Wiring diagram will confirm. If it does switch to earth a jumper lead to earth from the terminal will confirm (and light the brake lights).

 

The '78-'79 US 308 B/S schematic shows that you should have two single red (R) wires connected one each to the two male spade terminals of the brake light switch, and that the red-white (BR) wire that you presently have connected there should be going to the seat belt buzzer (the small gold box) next to it where that red wire is now (wrongly) connected. IMO, you should swap that R and BR wire, and then search for the other missing R wire .

One thing you could do is measure the voltage on that one red wire that you have relative to ground with the key "on":

1. If it is +12V = you've got to find the missing red wire that goes to the rear brake lights.

2. If it is not +12V = you could put +12V on it to see if the brake lights go "on" = so is the red wire going to the brake lights, and maybe someone has wrongly stolen the red wire with the +12V to do something like operate the radio. In your photo there seems to be a large (stock) red wire connected by an aftermarket connector to a (non-stock) small red wire. Another clue here would be if your seatbelt/key-left-in-ignition buzzer is not working = a sign that that existing red wire is the wire that goes to the brake lights.

Good Hunting!

 

That's not the best solution (although having brake lights rather than not having brake lights is a plus ). The "problem" with using the BR wire as the +12V source for the brake lights is that puts a large current thru the small switch (on the ignition switch) that detects the presence of the ignition key. This small switch is not designed to carry a large current and will probably frazzle after a short while. Would be far better to just run another (red) wire from the bottom of fuse #1 to be the +12V source for the brake light operation (as that's the stock design).