Highmount and license plate lights

[mrgmguy]

Buick Century 99

hi guys my highmount are out as well as my license light any idea ,i kno its not a fuse because

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[djdevon3]

Highmount is a brake light so it’s connected to the brake light circuit. Check the high mount harness wires. They can come loose. Since your brake lights work that’s actually a good sign that the entire circuit hasn’t shorted out and should be fairly easy to track down. The license plate light might just be a burnt bulb? Unless the license plate light gets its power from the high mount (unlikely) my guess is you are dealing with 2 separate issues.

[mrgmguy]

Any idea were i should start looking? i replaced highmount bulbs also if 1 bulb is burnt will the all of them not work

[Grayfox]

Quoted From mrgmguy:

Any idea were i should start looking? i replaced highmount bulbs also if 1 bulb is burnt will the all of them not work

Depends if they are wired in series or parallel.

A series is mainly for current and will most likely not be used for the CHMSL

a series looks like this

So if one bulb blows the circuit is incomplete and will not work.

A Parallel circuit focuses on voltage and will be the one that is most likely used in the CHMSL

A parallel circuit looks like this

so even if one bulb is blown the circuit is still complete and will continue to work.

[Grayfox]

Double post due to dial up speeds and high latency.

[mrgmguy]

i started the car up and plug a volt pen that lights up if thers power and nothing but my revers light work fine

[Grayfox]

My old cars CHMSL was spoiler mounted and their were 2 wires inside the boot that came from the spoiler and they were connected to the brake light.

[EricTheCarGuy]

If you replaced the bulbs and it’s still not working I think the next step is to see if you have power and ground at the socket itself. If you don’t have one or the other it’s time to break out a wiring diagram and trace the circuit back to the fault. To my knowledge they don’t often run a separate circuit for a 3rd brake light so I would suspect a problem between the tail lights and the high mount. Perhaps someone on the forum might have access to a wiring diagram for you. As for the license plate lights it MIGHT be related but perhaps only because the wires might run in the same harness somewhere, a wiring diagram would tell you if that is the case however.

[Author]

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