Both brake lights and 3rd light in back window fail to light when brake is applied. tail lights do work when headlights are on.

you wired it up wrong,
it worked before the modification to wrong parts

to fix this one uses the service manual first to see how the stock lamp work. (park/brake/turns)

then we examine how the alien lamps are wired
than we wire it up corectly
i can't see both of those facts or I would know the answer easy
no country told and the MC is sold all over earth
and street lighting laws are not the same all over earth not now or ever
if I was to put , European lamps my USA bike it will fail
or the reverse.
not saying I can not rewire any lamps to work. I sure can.

but I sure can not BLIND, ever, why ask the blind
ask a shop to rewire it, most any car or back electrics tech can do this blind folded.

No, your brake lamps should only work when brake pedal is activated. Your headlamp switch shouldn't have anything to do with brake lites.
Sometimes if there is a faulty ground, your lamps may act weird?
Did I miss-understand your post?

Did you change the radio recently..if so you tapped into the wrong wire...and if not then I would say you have a bad headlight switch or a broke ground dome where

will u have a few more switches and relays to check/change brake light switch and relay/and headlight switch

It may sound silly, but check your brake light bulbs to see if they have been installed incorrectly. Brake light bulbs have two filaments, one for tail light, and a brighter one for brake lights. On some cars if the bulb is installed wrong, the brighter filament will stay on for tail lights. The only other thing I can think of is the wrong bulbs have been installed.

It sounds as if you have a bad earth to either one or both of your rear light clusters. If it only happens when you indicate in one direction then that is the offending side.

you have a bad ground to the taillights , the signal is looping back to the front light grounds

I would check the wiring to the 2 side lights, and make sure they are grounded or none has been cut or corroded. You have good power going to the rear if the 3rd brake lite is working fine so I would trace the wire from the 3rd brake light to where it splits and goes to the 2 rear brake lights...

you might have an open ground wire on your brake/tail lights .. when you apply the brakes then power would flow thru the brake light (not see ground) so would then provide power backwards thru the parking light (common ground open) to all the other things connected to the parking lights .. like the other parking lights and dash ... when you turn power on to those things (headlights on) then there is 12 volts on both sides of the light .. thats why the lights quit working ... if the missing ground is the problem then most of the lights that are improperly turning on should be at a lowered brightness level.. interesting problem .. its also possible to have a brake light bulb that has the common ground open inside or not making connection with its socket .. i would start by removing the brake lamps and see if the problem goes away .. if it does look for a broken ground or damaged lamp ..

Hi,

Often brake lights and signal lights not working indicates a loose grounding of the rear electrical assembly. Other indicators would be dim and/or all the lights light up (but dimly) when engaging the breaks or activating any of the turn indicators. A way to verify this is to hardwire another/external grounding wire to any of the metal receptacles of the bulbs straight to a bare metal/chassis of the vehicle.

Of course the standard procedure of checking the fuses, the harness connectors and the wire harness themselves still apply.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

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