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Hydraulic Brake Switch And Rear Brake Lights


Best Answer GraemeC , 24 August 2021 - 01:49 PM

The brake light switch should receive 12V on a green cable from the fused side of fuse 3/4 .  It will only be live with the ignition switched on.
On the other terminal of the brake switch should be a green/purple which sends the voltage to the brake lights.

 

With ignition on, touching the wires together should illuminate the lamps.

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#1 mx5nut

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Posted 24 August 2021 - 12:56 PM

After bleeding the brakes (see related post from today), I happened to notice that the brake lights don't come on even though the pedal has a nice firm feel and there are no apparent leaks.  All tail lights, turn signals, and license plate lights work, so I am thinking it is isolated to the brak lights and not an issue with the whole rear part of the harness.  When I looked down at the brake switch, the connections were kind of loose and there was a tiny spring that looks like it had dislodged from the switch.  I am sure the switch is part of the problem and I plan to replace it, but I am also worried about the wiring as well.

 

After doing some searching of my own on the topic, I read some other posts where people had touched the two wires together and the brake lights come on.  When I did that last night, my brake lights did not come on.  As luck would have it, my circuit tester broke in my hand, so I haven't been able to test for electricity all the way to the switch.  However, if I  touch the two wires together and no brake lights come on, doesn't that give me some indication that there is not electricity getting to the switch and there could be a problem elsewhere in the harness?

 

The idea that there is something wrong elsewhere in the harness is what worries me, since I don't have much experience with the harness and dealing with electrical issues in general. 

 

Given my lack of experience, I guess I am asking if you more experienced people can help guide me in terms of what to look for next, so I can try to trace back to the root cause of the brake lights not working.



#2 GraemeC

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Posted 24 August 2021 - 01:49 PM   Best Answer

The brake light switch should receive 12V on a green cable from the fused side of fuse 3/4 .  It will only be live with the ignition switched on.
On the other terminal of the brake switch should be a green/purple which sends the voltage to the brake lights.

 

With ignition on, touching the wires together should illuminate the lamps.



#3 mx5nut

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Posted 24 August 2021 - 02:02 PM

The brake light switch should receive 12V on a green cable from the fused side of fuse 3/4 .  It will only be live with the ignition switched on.
On the other terminal of the brake switch should be a green/purple which sends the voltage to the brake lights.

 

With ignition on, touching the wires together should illuminate the lamps.

 

I think my stupid mistake may have been that I didn't have the ignition on at the time.  I will try again with ignition on later today and report back if issues persist.



#4 riktanius

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Posted 24 August 2021 - 02:48 PM

On a side note, is there a How-to for switching to a normal brake switch (activated by the pedal moving)?



#5 mx5nut

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Posted 24 August 2021 - 05:34 PM

Ok with ignition on, brake lights worked when I touched the wires together, which tells me that it is just the switch. Phew!

#6 Spider

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Posted 24 August 2021 - 08:05 PM

On a side note, is there a How-to for switching to a normal brake switch (activated by the pedal moving)?

 

There isn't (yet) a 'How To', but there are a few threads on the subject and one not too long ago. Beardylondon had a very simple yet effective solution in that.

 

https://www.theminif...c-post-76-type/

 



#7 bpirie1000

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Posted 25 August 2021 - 10:44 AM

Just remember that you can not just remove the pressure switch and plumb the new one or your brakes will have no pressure..

And stopping i suspect will be a bigger issue for you...

#8 mx5nut

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Posted 25 August 2021 - 05:39 PM

Just remember that you can not just remove the pressure switch and plumb the new one or your brakes will have no pressure..

And stopping i suspect will be a bigger issue for you...


Are you referring to a need to bleed the brakes again after installing a new switch?

#9 sonscar

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Posted 25 August 2021 - 06:03 PM

I think he meant if you remove it and leave a hole,Steve..

#10 bpirie1000

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Posted 28 August 2021 - 08:00 PM

Both above really.....




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