Tail/brake light bulb

erjdriver said:

I bought these to replace my rear brake lights.

Amazon

The red-brilliant variant.

It works but when I turn the headlights on, the tail lights come on as if the brakes are pressed - including the third tail gate brake light - all at high intensity.

With the headlights off, they function normally. low intensity normally and with the brake pedal pressed - high intensity lights come on.

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Try flipping them over, i.e. rotate 180 degrees in the socket.

FKHeath said:

Try flipping them over, i.e. rotate 180 degrees in the socket.

Click to expand...

I did - all four combinations.

When the headlights are on, the tail-lights are supposed to be on also. So the car is sending a reduced voltage or current to the bulbs. When the brakes are pressed, sends the full voltage/current - i'm thinking current. But since these are very low current bulbs - they go full brightness at even the lower setting.

These bulbs are 3 watts. The oem sylvania 7443 bulbs are 25 watts.

So looks like most probably resistors that reduce the current are needed.

erjdriver said:

I did - all four combinations.

When the headlights are on, the tail-lights are supposed to be on also. So the car is sending a reduced voltage or current to the bulbs. When the brakes are pressed, sends the full voltage/current - i'm thinking current. But since these are very low current bulbs - they go full brightness at even the lower setting.

These bulbs are 3 watts. The oem sylvania 7443 bulbs are 25 watts.

So looks like most probably resistors that reduce the current are needed.

Click to expand...

The 7443 incandescent bulb has two filaments, a 5.9 watt for tail light and an 25 watt for brake or turn signal. The car does not send a lower voltage for the dimmer tail light, rather it sends the normal 12 volt but only to the 5.9 wall filament for the tail light. Thus, your presumption is wrong. The LED versions should have a lower brightness if the correct contact is made.

Many of these after market LED lights have a poor contact configuration for the terminals, and the connection within the socket can be wrong. Suggest you get a reliable brand such as Lasfit which should have good, proper contacts. Or another possibility is your lower brightness part of the LED is too bright, so it seems that the brake light is on when really the lower brightness is on. I would never butcher my wiring by adding a resistor, when the problem is in the light bulb you have added. Leave the wiring alone and get a light bulb that works right.

Just get the right bulb. Modifying stuff is just asking for problems, either immediately, or down the road.

FKHeath said:

The car does not send a lower voltage for the dimmer tail light, rather it sends the normal 12 volt but only to the 5.9 wall filament for the tail light.

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Just curious as to how it sends voltage to just the 5.9 filament. I only see two wires going into the socket. Of course there could be two wires in each.

Yes I put in a Sylvania incandescent 7443 bulb and everything is back to normal.

erjdriver said:

Just curious as to how it sends voltage to just the 5.9 filament. I only see two wires going into the socket. Of course there could be two wires in each.

Yes I put in a Sylvania incandescent 7443 bulb and everything is back to normal.

Click to expand...

This may help:
And this:

My thoughts: the 7443 is a dual filament, correct? What was linked is a bulb that allegedly works as a 7443 and a 7440 (single filament). What may be happening is the LED bulb when installed is short-circuiting, per se, the brake lighting system as well. So when the power for the headlights/taillights is on, the bulb is sending the power through the brake lighting as well.
Since the OP has determined that an incandescent bulb allows the systems to operate as normal, the issue is with the LED bulb purchased and installed.