Need some help with LED conversion on 04 GT

FATTS_DC · Feb 10, 2025

So I decided to replace all the stock bulbs on my 2004 Mustang GT with LED. I first started with the gauge cluster, I bought these from Amazon and they worked fine, except one of the bulbs replaced wasn't working, maybe switch the bulb around or replace it with a new LED, it is not a big deal. I'm still waiting for more LED bulbs to arrive. The next bulbs I replaced were all the interior lights, and after testing everything after replacing them, they all worked fine, with no issues. The next bulbs I replaced are the front turn signals, I tested them after the installation, and again, they are working fine. I then proceeded to the rear tail lights. I replaced the three bulbs on each side. I tested this and I ran into something weird... I didn't notice it at first, but I later noticed that instead of the tic, tic, tic sound normally from a turn signal, there was also this buzzing sound every time the signal blinked. It if is left on for a few seconds, the blinking either stays on with no more blinking, but still buzzing. Sometimes the blinking would be spiritic and inconsistent.

Does this mean the signal relay went bad? Or is this the case of needed load resistors? I tried looking for similar issues that someone else may have posted on YouTube or other forums, but they never mention the buzzing sound, they do mention the inconsistent flashing and sometimes just on with no blinking. If it is the relay, where is this located? If I don't need load resistors, do I buy one for each LED I install? or just the rear Tali lights since that's where the issues started?

Noobz347 · Feb 10, 2025

Put the OEM bulbs back in the car.

Your LEDs are likely not pulling the current necessary to make everything work correctly. I guess that LED bulbs exist that are supposed to work but most of what I've seen indicate that they generally create more problems.

PSKSAM2 · Apr 23, 2025

FATTS_DC said:
So I decided to replace all the stock bulbs on my 2004 Mustang GT with LED. I first started with the gauge cluster, I bought these from Amazon and they worked fine, except one of the bulbs replaced wasn't working, maybe switch the bulb around or replace it with a new LED, it is not a big deal. I'm still waiting for more LED bulbs to arrive. The next bulbs I replaced were all the interior lights, and after testing everything after replacing them, they all worked fine, with no issues. The next bulbs I replaced are the front turn signals, I tested them after the installation, and again, they are working fine. I then proceeded to the rear tail lights. I replaced the three bulbs on each side. I tested this and I ran into something weird... I didn't notice it at first, but I later noticed that instead of the tic, tic, tic sound normally from a turn signal, there was also this buzzing sound every time the signal blinked. It if is left on for a few seconds, the blinking either stays on with no more blinking, but still buzzing. Sometimes the blinking would be spiritic and inconsistent.

Does this mean the signal relay went bad? Or is this the case of needed load resistors? I tried looking for similar issues that someone else may have posted on YouTube or other forums, but they never mention the buzzing sound, they do mention the inconsistent flashing and sometimes just on with no blinking. If it is the relay, where is this located? If I don't need load resistors, do I buy one for each LED I install? or just the rear Tali lights since that's where the issues started?

Odd that you got a buzzing, usually the symptom on an LED turn signal change is "hyperblink". The stock flasher is designed to detect the amount of current used for incandescent bulbs, and blink faster if a bulbs are out. LEDs use less current, so you either need load resistors that pull current in parallel with the LED bulbs or a flasher relay that handles LED bulbs and will not hyperblink. Could be that the combination you've got in there is causing an odd hyperblink that sounds like a buzz? I've changed my blinkers/brake lights to LED bulbs, no resistors, and changed the relay to an EP27 and have not had an issue. The relay is clipped up behind the dash on the drivers' side, it is what you hear the "clicking" coming from when you turn on the turn signal normally.

I'd say you could either swap back to stock incandescent and see if it returns to normal, or replace the flasher relay with and LED capable one and see if it starts working.

stormsedge · Apr 24, 2025

I’ve stayed away from the LED kits bc some require additional relays/resistors/who knows what to work correctly. Go back and look at the paper trail on your bulbs to see of there are missing parts. Happy hunting.

Need some help with LED conversion on 04 GT

FATTS_DC

Member

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

PSKSAM2

stormsedge

Similar threads

Need some help with LED conversion on 04 GT

FATTS_DC

Member

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

PSKSAM2

stormsedge

Similar threads

Privacy & Transparency

Privacy & Transparency