are brake lights & headlights linked?

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morgan73
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are brake lights & headlights linked?

Post by morgan73 »

Help! My brake bulb needed changing. I did that and now every time I brake my headlights come on as well. What have I done? How the hell did that happen?!
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JohnD
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Post by JohnD »

I would start by removing the bulb that's just been replaced, and try again, making sure it's the right way round and sitting correctly across the two contact points.
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AndersDK
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Post by AndersDK »

In line with John -
Have you fitted a single filament bulb, in a 2-filament bulb socket ?
morgan73
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Post by morgan73 »

I bought a twin pack of bulbs about 6 months ago when I needed one for the other side. I used that and had no problems so I assume the bulb's the right one.
chemexhants
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Post by chemexhants »

Anders is quite correct. The bulb you have replaced should be a twin filament unit for tail and brake light. By replacing it with a single filament bulb, when the brake pedal is pressed the current can only activate the tail light circuit which, by creating a short circuit, also activates the headlamp on the side that you have replaced the bulb.
Change the bulb to a twin filament one and the problem will be resolved, and you will not be flashing at too many other drivers!!!
morgan73
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Post by morgan73 »

Thanks everyone. I've changed the bulb (it was single filament) and everything works fine now. I still can't figure out why it worked ok in the other side though [?]
JohnD
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Post by JohnD »

But a single filament bulb wouldn't work correctly. The correct bulb is a 21/5. 21 for the brake light and 5 for rear light.
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