Brake light question

My 1978 Ford Granada has the dual filament bulb for the brake light. My question is this: do both filaments ever light at the same time? When I
depress the brake pedal I see the high intensity filament light up only.
Thanks in advance
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Dual filament bulbs, one for tail light, other for stop light. At night when lights are on, hit the brake, both filaments are lit.....
Azazel Scratch wrote:

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snipped-for-privacy@tampabay.rr.com says...

One issue may happen if the ground is poor. The current may try to run through both filaments. It may work as a tail light, or a brake light, as it grounds through the other filament, which is often tied to another bulb that provides a path to ground. But when it tries to do both, it turns off as both are getting 12V.
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some rear lights are dual filament .. for running light and turn signal.
some real lights are dual filament .. for running light and brake light.
turn on headlights ... so the running lights switch on ... and then hit the turn switch or brake switch ... to see if it is working properly.
errr ... the grounding of the DC volts are going where it is suppose to go ... and not somewhere else from corrosion or crack failure.
sumbuddie hopes that helps
:?
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