Using a resistor for LED lights?

[Bgunner]

How can you figure out what the proper resistor you need is when using LED bulbs?

Issue: 3rd brake light staying on dim but only when the ignition is on.

I just ordered 2 more gaskets for the light so I can remove it and test one time and one to insert the proper resistor if that is the issue.

Testing will consist of hooking up the original and seeing if it is on, If not it needs a resistor, if yes then I need to find the bad ground.

The real question is how do I know what resistor I will need to help break the grounds contact just enough to shut off the light but still allow it to make a connection when the pedal is pushed? I know nothing about resistors and there ratings so some guidance is needed.

 

[cbxer55]

The LED third brake light I installed on my Mustang does that, very dim all the time but super bright when the brakes are applied. I am just going to leave it that way, it's so dim it's not a problem to me. The LED tail lights I put on it came all wired with all the proper stuff so they were just plug-and-play.

 

[adsm08]

The Sylvania ballast resistors for automotive LEDs should work fine. Your average light bulb is only 1-2 ohms of resistance, an LED shouldn't need more than that as a ballast.

 

[RonD]

"Resistance is futile" signed The Borg

I think Dirtman is rubbing off on me

 

[Bgunner]

@adsm08 I googled the Sylvania ballast resistor but didn't see any that specifically said ballast from them but I did see this one: Sylvania Load resistors for LED Mini bulbs 12V - 6 ohm .

Is this what you are referring to or the the ceramic ballast's that also came up in the search?

Is 6 ohm to much since you mentioned that the standard bulbs are around 2 ohms?

 

[Bgunner]

The LED third brake light I installed on my Mustang does that, very dim all the time but super bright when the brakes are applied. I am just going to leave it that way, it's so dim it's not a problem to me. The LED tail lights I put on it came all wired with all the proper stuff so they were just plug-and-play.

My LED tail lights came with the ballast pack and were a plug and play, no fuss system, sort of as I needed to reverse the ground and power wires since mine is the 94 and not the 98 and newer, but the 3rd stop lamp didn't and none of the ones I saw for sale came with the resistor/ballast. If it wasn't so noticeable I'd leave it alone but it really stands out at night. When I hit the pedal its very bright and you can see the difference easily but I know its not right and want to fix it.

 

[Dirtman]

Kinda odd, never had that issue with the LED third brake light on mine. Dunno what the difference would be between them?

 

[adsm08]

Sylvania Load resistors for LED Mini bulbs 12V - 6 ohm .

Yeah, that thing.

 

[Bgunner]

Kinda odd, never had that issue with the LED third brake light on mine. Dunno what the difference would be between them?

I don't know what the difference would be either. Maybe yours uses the power wire at the brake switch instead of the the ground like mine? Could also be a different brand that draws more or has a higher internal resistance.

I'll order up those resistors tomorrow and pull the light as soon as the gaskets come in. I'll plug in the beat up old one to see if the bulb comes on, which I'm pretty sure it wont but its best to check first, to be sure the resistors will do what is needed.

On my friends '08 F-250 the interior ceiling light would not go out with an LED bulb in it. It would stay on but dim also. It got changed out to a different brand LED bulb and it went out like it should so this could be the issue I am experiencing now where the resistance of the bulb is enough to not light it but with an LED the resistance is lower allowing it to light up dimly.

 

[cbxer55]

I've had a LED third brake light in my 98 Ranger for 18 years, never had an issue with it. Except last time I backed up to a glass window to check the brake lights (I do this somewhat regularly in all my vehicles at the dead mall a mile from where I live), I noticed that only three of the six LEDs are lightning up now. So time to order up a new one from CARiD. I have it on my Ranger wish list.

 

[gw33gp]

I recently replace the standard bulbs for the tail and brake lights on my 69 Fairlane Cobra with LED lights from Super Brite LEDs. They are a direct replacement and require no ballast or resistor. I have heard that sometimes the flasher must be replaced for the turn signals but mine work the same as they did before the replacement. They have many bulbs to choose from and you should be able to find one from them for your application. They are much brighter than the standard bulbs which were very dim on my old Cobra.

 

[Bgunner]

I recently replace the standard bulbs for the tail and brake lights on my 69 Fairlane Cobra with LED lights from Super Brite LEDs. They are a direct replacement and require no ballast or resistor. I have heard that sometimes the flasher must be replaced for the turn signals but mine work the same as they did before the replacement. They have many bulbs to choose from and you should be able to find one from them for your application. They are much brighter than the standard bulbs which were very dim on my old Cobra.

That's good to know. In my case the whole 3rd stop light is replaced and not just the bulb. I did this because the original's casing was melted from the bulb being on for a long time causing a sag and split in the casing. I had a hard time removing the original casing due to it being larger than the opening due to the sagging.

 

[Dirtman]

I recently replace the standard bulbs for the tail and brake lights on my 69 Fairlane Cobra with LED lights from Super Brite LEDs. They are a direct replacement and require no ballast or resistor. I have heard that sometimes the flasher must be replaced for the turn signals but mine work the same as they did before the replacement. They have many bulbs to choose from and you should be able to find one from them for your application. They are much brighter than the standard bulbs which were very dim on my old Cobra.

The flasher thing depends entirely on whether or not you have a thermal or electronic flasher relay. Electronic flashers aren't effected by the bulb type unless they also include a bulb out indicator.

 

[RonD]

The flasher thing depends entirely on whether or not you have a thermal or electronic flasher relay. Electronic flashers aren't effected by the bulb type unless they also include a bulb out indicator.

That was a very thought out and reasoned response

I thought you were drunk and it was Tuesday?

 

[Dirtman]

That was a very thought out and reasoned response

I thought you were drunk and it was Tuesday?

Im currently at phase 2 drunk. I can still be quite articulate at this phase in the process. You won't see a marked increase in grammatical error or any decline in advanced reasoning ability until phase 3. At phase 4 rational thought begins a steep decline and my posts will most likely become rambling. By stage 5 anything I post will be merely jibberish if I am even able to type at all.