Third brake light

[hammersmith]

Hi,
I have fitted an internal third brake light, which works when the brake pedal is depressed, however when releasing the pedal there is still a dim light showing. Can anyone assist with why this is. TIA
Mike

[les]

Pressure from the system maybe, I suppose it depends how you linked it to the circuit.

[simmitc]

Presumably the third lamp is an LED unit, and your original lights still use the standard tungsten filament bulbs? If so, it is possible that the brake light switch is still making a very slight contact but the current being passed is not sufficient to illuminate the normal bulbs, but is just enough to show in the LEDs.

Disconnect the wires from the brake light switch. Does the third light extinguish. Join the wire together, all three lights come on, disconnect wires, all three lights go out correctly.

It is possible to start checking with a meter, but the above test should confirm if a new switch will solve your problem.

[hammersmith]

Hi many thanks I have led in the rear red lights. But I will try your suggestion. Many thanks Mike

[King Kenny]

I have a similar problem with LED internal lights. I read somewhere that because LEDs use less current they are sensitive to stray currents. Apparently the excess current is flowing through ordinary bulbs all the time (as leakage) but is not enough to make the bulb glow. The writer suggested fitting a standard bulb or a resistor in the circuit to remove excess current would stop the LEDs from glowing. As It is the internal light I have not tried this.

[geoberni]

Hi many thanks I have led in the rear red lights. But I will try your suggestion. Many thanks Mike

I'm guessing they're different LED lamps in the Rear Lights from the one you've got in the 3rd Lamp?
Different LED Lamps have different build characteristics. The actual LED itself requires around 2-3 volts, and will go 'Phut' at about 5v.
So to buy them typically offering to work at 12-24v for vehicle use, they have a voltage control circuit. Depending on the quality of the lamp manufacture, some will block any lower voltages some won't.
I'm guessing that your 3rd lamp isn't and there's a stray volt or two getting through somewhere.

[hammersmith]

Hi many thanks. Mike

[svenedin]

I fitted an LED bulb in the tell tale on the end of the indicator stalk. It flashes dimly and very briefly when the ignition is turned on so yes they are sensitive to stray currents which would not cause an ordinary incandescent bulb to glow.

Stephen