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I found the third brake light burned out, will this cause all brake lights not to work?

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Brake lights are wired to work independently for safety reasons. If none of the lights are working, the first thing to do is check all the bulbs are good. No reason to start chasing wires if the bulbs are bad.

If all the bulbs are good, check fuses. If fuses are good, use a multi-meter to check for power at the light socket.

If no power, then check the brake light switch by the brake pedal.

Most common cause of these problems are bulbs, fuses, or the switch.

  • Are they truly independant? 3 fuses, 3 switches and 3 wires to the rear? I know side or marker lights are split and fused left and right... same for headlights - relatively recent though... – Solar Mike May 17 '18 at 13:49
  • @SolarMike - I think he means they are not in series where if one goes out, the rest are left without power. I believe you are right that they are powered from the same source, with the same switch, through the same fuse. – Pᴀᴜʟsᴛᴇʀ2 May 17 '18 at 14:37
  • @Pᴀᴜʟsᴛᴇʀ2 I don't know of any bulbs on a car that are wired in series unless it's led's for interior... but stop, indicator, marker, headlight are all parallel as voltage stays the same while as soon as you go series the supply voltage needs to increase i.e. 2 12v bulbs in series need 24v or they are much dimmer... – Solar Mike May 17 '18 at 14:47
  • @SolarMike I think you know what I meant by my answer. I did not mean truly Independent. It was a simple way of wording it. We can't make the assumption the OP knows the lights are not wired in series. Nor can we assume all the bulbs are good. Many people never check their tail/brake lights. I have seen people change everything but the bulbs, when it was the bulbs. :-) – CharlieRB May 17 '18 at 15:36
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Here is your brake light wiring diagram, might help you diagnose and answer some of your questions.

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No, if the third is not working as it has blown then the others can still work if the supply, switch and fuse are all ok.

If none of them work, you have to check fuse, supply to switch, supply from switch and feed to the rear.

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