Hi guys,
Long time no post. Thanks for any help with the following issue.
I have a 04 FX4SCREW. Recently I replaced all rear exterior bulbs with LED's from JDM Astar (Amazon seller). I am suffering from a issue that I have searched here and other forums for.
When my lights (running/parking or headlights) are turned off the brake lights function normally (off and full bright when pedal applied).
However if I turn my running/parking or head lights "On" the running/parking lights on the rear are FULL bright, like they are getting full voltage?
When I apply the brake pedal there is a tiny almost not noticeable change in intensity.
Third Brake light works correctly and the issue was present with the running lights before I switched it to an LED bulb.
What could be the cause of the full voltage for the running /parking portion of the light? They are installed correctly as I have turned them and they did not function at all so polarity is correct. Also it doesn't matter if it is only 1 installed or both sides, no difference.
Do I need "load resistors" to reduce the voltage on the running/parking side? If so what wires to I install the load resistors across? Do I need to size the load resistors or is there a specific one that will work that I can buy?
Do they sell LED 3157 with pre-installed load resistors or voltage reducers?

If someone needs I can take pictures and upload them.

I had the standard hyperlinking issue that I at first didn't mind but fixed with a new blinker relay information I found posted here. So I don't have hyper blink, I fixed that after getting stopped for equipment violation (fishing for "other" violations) and having to prove in all of the nice state troopers scenarios that all of my lights were functioning properly just not in the "standard and expected manner" leaving him slightly irritated and frustrated that I wasn't a drug runner.

 

Whoa, there! You stated If that is the case, that the problem existed with standard incandescent bulbs, all the LED stuff is irrelevant. Go back to the standard bulbs and troubleshoot it that way. Once repaired, then go back to the LEDs.

Clarify.

Is your 04 a "Heritage" (Leftover 03) or an NBS? The circuits are slightly different between generations.

Have you owned this truck since new or did you buy it with this issue or did it develop after acquisition?

 

To clarify:
Truck is an 04 FX4SCREW NBS, owned since mile 000004

When I install 3157 incandescent in the taillight fixture all lights function properly. Running lights are dimmed and brake lights are bright.

When I install LED 3157 equivalents running lights are full bright, brake lights are full bright.

The statement you quoted left out the beginning of the sentence THIRD BRAKE LIGHT" ("Third Brake light works correctly and the issue was present with the running lights before I switched it to an LED bulb).
So the Third 3rd Brake light being incandescent or LED has no effect on the running lights being bright all the time with LED's installed.

It seems as if when the running lights are on with LED they are getting full voltage.
I know the computer notices when the LED is installed and causes the hyper blink because of the load difference.
Does the computer also think there is a bulb missing and apply full voltage for the running lights when and LED is installed?

 

its not "full voltage"...... there are two elements inside the bulb.. one is the tail light and it is "dim" and the other is the brake / turn light and it is "bright"..... if the system works with the standard bulb and you get the BRIGHT light on the tail light when you install the LED, then the LED bulb is bad or the wires are on the wrong terminals. are you using the original wire harness plug or did you rewire to the LED lense.

 

Original harness just unplugged standard bulb and plugged in LED checked polarity by reversing LED and did not function at all in one direction and was full bright 180 deg turned.

Guess I will try a different type and see if that fixes it.

 

Return or junk the Amazon tail/stop light LEDs. Replace the with incandescent bulbs or properly functioning LEDs.