Hi all,

I have a Mini One Convertible 04 plate and none of the brake lights are working. My partner has changed the bulbs, new brake light switch, checked the fuses, we bought a new ecu module, he has checked all the earthing, and wiring, all fine but nothing has worked.

Anything else we are missing?

Thanks

 

Fuses need to be properly checked for operation. A fuse can look ok but still be bad. A volt/ohm meter or continuity tester is better than eyeballing...

(In a pinch a similar fuse from another circuit, a circuit that is known to work, can be exchanged with the brake light fuse.)

Believe the usual set up is when the brake pedal is depressed this causes a stop to move away from the brake light switch plunger and this closes the switch and the lights come on. Without being at the car or having access to a wiring diagram I'm thinking the brake lights are already powered so the switch closes a ground which then turns on the brake lights. This is a "fail safe" setup.

Assuming the brake light circuit has power and the switch controls the ground checking if there is power to the brake light at the socket I think would be justified.

Also, one wants to observe the operation of the switch to ensure that as the brake pedal is depressed and the stop moves away from the switch the switch plunger moves out and its movement is not interfered with by something hanging down in its way.

 

Forgive me for asking a dumb question but are you/he using a volt meter to check output voltage at the wiring harness? Do you have tail lights and do the blinkers work?

I don’t have the diagram for the wiring harness, but you can find it on line. There will be a hot wire for the brake light in the harness that plugs into the tail light assembly. It should have zero voltage when the brake is off and then show 12 V when you step on the pedal with the key on.

if you have 12 v at the fuse panel and 12v going into the brake switch, that’s good. Check that there is 12v coming out of the switch when you depress the pedal with the key on. If so, then check the wire going to the brake light when the key is on and the pedal is depressed.

if you have 12v coming out of the switch w key on and pedal depressed, but no voltage at the bulb harness, then you have a break in the wiring.

if you have 12v at the wire, then check that you have 12v at the base of the bulb holder. Look at the bulb holder (w bulb out) and put the red test lead on the shiny dot at the bottom. There should be 12 v there when you step on the brake.

Also check the bulb holder for continuity w ground. Put one test lead on the body of the bulb holder and the other lead on ground (while plugged into harness) You should have zero ohms resistance. It it shows up w much more than that, you have corrosion on the bulb holder ground ​​​. If you have no reading at all, then you have a bad ground wire/bad bulb holder.

good luck and let me know what you find. You can pick up a good cheap voltmeter at Harbor Freight if you don’t have one

 

Hi,

yes he is using a voltage meter to check all the outputs and we bought a mini booklet with the wiring diagram inside. Still no luck.

He has done every test possible on the wiring, bulbs, voltages are all fine and normal.

He has been reading up and others are saying it could be something to do with ABS?

 

So, looking at the book, I see a blue & red wire that comes off of the brake light switch that feeds power to both the ABS & something called the General Control Unit (#14 in the upper diagram)

Use the key in pic #2 to help decipher the parts and wire colors in pic #1

So I interpret the diagram to show that the ABS and the lights are separate. Is your ABS light on?

Did you check to see if there is 12v at the wiring harness that plugs into the brake/tail light assembly (w key on and pedal depressed)? You need to remove the entire light assembly from the car. Just let it dangle from the wires (still plugged into the light assembly) That way you can probe the wires from the back of the harness.

you’re looking for the black & yellow wire (Sw/Ge in the diagram) or the black & blue (Sw/Bl) wire on the harness