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Simple Circuit Help- Automotive Lighting Circuit

M

Matt

Jan 1, 1970
0
Hi All, I'm hoping someone can help me, i have what is probably a simple
problem-

My car (Mitsubishi) has a dual filament stop/tail light for each of the rear
lights (12v 5/21w), and a 3rd LED highlevel brake light.

Incase your not familar with this setup due to this being an international
newsgroup and i'm in the UK, when you turn your headlights on, the 'tail'
light filament of the bulb illuminates (5w) and illuminates the red section
of the rear cluster. When you press the brake pedal, the 'stop' light
filament of the bulb illuminates (21w) and the red section of the rear
cluster illminates brighter, also the red LED brake light illminates.

I wish to replace the stop/tail light bulbs with LED items, these i have
bought and fitted, however they give the following issue-

They work fine in the cluster for stop/tail operations, but when in the tail
light only (Lights on, but the brake pedal not depressed) a few LEDs in the
high level brake light illminate dimly, if i replace the LED bulbs with the
filament ones the LED remains extinguished in tail light only.

Does anyone know why this is happening? I assume its something to do with
the LED bulbs having lower resistance than the filament counterparts so some
voltage is 'leaking' through to them? Can i put a resistor in the line of
the power to the high level brake light to solve this? If so what value of
resistor would you suggest?

Thanks for any and all help

Matt
 
T

Tom Biasi

Jan 1, 1970
0
Matt said:
Hi All, I'm hoping someone can help me, i have what is probably a simple
problem-

My car (Mitsubishi) has a dual filament stop/tail light for each of the
rear lights (12v 5/21w), and a 3rd LED highlevel brake light.

Incase your not familar with this setup due to this being an international
newsgroup and i'm in the UK, when you turn your headlights on, the 'tail'
light filament of the bulb illuminates (5w) and illuminates the red
section of the rear cluster. When you press the brake pedal, the 'stop'
light filament of the bulb illuminates (21w) and the red section of the
rear cluster illminates brighter, also the red LED brake light illminates.

I wish to replace the stop/tail light bulbs with LED items, these i have
bought and fitted, however they give the following issue-

They work fine in the cluster for stop/tail operations, but when in the
tail light only (Lights on, but the brake pedal not depressed) a few LEDs
in the high level brake light illminate dimly, if i replace the LED bulbs
with the filament ones the LED remains extinguished in tail light only.

Does anyone know why this is happening? I assume its something to do with
the LED bulbs having lower resistance than the filament counterparts so
some voltage is 'leaking' through to them? Can i put a resistor in the
line of the power to the high level brake light to solve this? If so what
value of resistor would you suggest?

Thanks for any and all help

Matt

If you purchased LED replacements for your cars tail/break lights they
should work just by installing them. No resistors or magic wands should be
necessary.
When you say some LEDs are dim, isn't that the way they are supposed to be
in the non-breaking condition?

Tom
 
R

Rich Grise

Jan 1, 1970
0
Hi All, I'm hoping someone can help me, i have what is probably a simple
problem-

My car (Mitsubishi) has a dual filament stop/tail light for each of the rear
lights (12v 5/21w), and a 3rd LED highlevel brake light.

Incase your not familar with this setup due to this being an international
newsgroup and i'm in the UK, when you turn your headlights on, the 'tail'
light filament of the bulb illuminates (5w) and illuminates the red section
of the rear cluster. When you press the brake pedal, the 'stop' light
filament of the bulb illuminates (21w) and the red section of the rear
cluster illminates brighter, also the red LED brake light illminates.

I wish to replace the stop/tail light bulbs with LED items, these i have
bought and fitted, however they give the following issue-

They work fine in the cluster for stop/tail operations, but when in the tail
light only (Lights on, but the brake pedal not depressed) a few LEDs in the
high level brake light illminate dimly, if i replace the LED bulbs with the
filament ones the LED remains extinguished in tail light only.

Does anyone know why this is happening? I assume its something to do with
the LED bulbs having lower resistance than the filament counterparts so some
voltage is 'leaking' through to them? Can i put a resistor in the line of
the power to the high level brake light to solve this? If so what value of
resistor would you suggest?

Thanks for any and all help

Where are you picking up the +12 for the third brake light? You might need
an isolation diode - can you draw a simple ASCII diagram of how things are
hooked up now?

And, FWIW, the "tail" and "stop" light arrangement is pretty much the same
as we do it in the US, and probably most cars around the world; they might
use different words in different countries, but the effect is the same.

Sometimes the "tail" lights are called "running lights" which would be in
parallel with the "parking lights".

What this leads up to is that there could be a miswire someplace, but to
really understand the situation I'd need a diagram or something. (I think
I'm half right-brained. ;-) )

Good Luck!
Rich

Rich
 
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