Tail Light LED Conversion
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Tail Light LED Conversion
Hi all,
I'm a new member on this forum, I've got a 2002 Blazer 4-door, 4.3L Vortec. When I first bought this truck, I put new tail light covers on it, but I never made the switch to LED's. Last night I was driving for quite a while, and sat in the drive thru for a long period of time, with my brake lights on. This morning I went to leave for work, and one of my tail lights was burned out, and the light cover around it was slightly melted. Right now I'm not sure if this is due to the halogen bulb burning too bright or if maybe it's just been the hot and sunny weather in my neck of the woods. I also just installed a new alternator last week, so I figured that could also be contributing to the lights burning hot. Regardless, I'm planning on switching my reverse, brake/running, and turn signal lights to LED. I've searched this forum and I keep seeing posts with mixed results. Some people say you can throw LED's in directly, others say you need a load resistor, and some are saying to use an LED relay. The people suggesting load resistors scare me because I don't fully understand the circuit for all the lights, and apparently if you wire too many load resistors in, or put them on the wrong parts of the circuit, you can melt wires or even start your rig on fire. I'd be willing to switch to an LED relay, but I've never done that before, and I don't want to switch my front lights to LED if a relay would require that. If anyone could explain a little about switching to rear LED's and maybe break down the concept of a LED relay, I would appreciate the enlightenment.
I'm a new member on this forum, I've got a 2002 Blazer 4-door, 4.3L Vortec. When I first bought this truck, I put new tail light covers on it, but I never made the switch to LED's. Last night I was driving for quite a while, and sat in the drive thru for a long period of time, with my brake lights on. This morning I went to leave for work, and one of my tail lights was burned out, and the light cover around it was slightly melted. Right now I'm not sure if this is due to the halogen bulb burning too bright or if maybe it's just been the hot and sunny weather in my neck of the woods. I also just installed a new alternator last week, so I figured that could also be contributing to the lights burning hot. Regardless, I'm planning on switching my reverse, brake/running, and turn signal lights to LED. I've searched this forum and I keep seeing posts with mixed results. Some people say you can throw LED's in directly, others say you need a load resistor, and some are saying to use an LED relay. The people suggesting load resistors scare me because I don't fully understand the circuit for all the lights, and apparently if you wire too many load resistors in, or put them on the wrong parts of the circuit, you can melt wires or even start your rig on fire. I'd be willing to switch to an LED relay, but I've never done that before, and I don't want to switch my front lights to LED if a relay would require that. If anyone could explain a little about switching to rear LED's and maybe break down the concept of a LED relay, I would appreciate the enlightenment.
Super Member
Joined: Apr 2014
Posts: 1,968
From: Lake City, Florida
Welcome to the forum!
First off I'll start with my solution. It's a little more involved, but it's been flawless for several years now.
https://blazerforum.com/forum/lighti...etrofit-90983/
In regards to load resistors and LED flasher relays, here's my experience. With LED's only installed in the tail lights and no other modifications, you will get a fast flashing turn signal. The easy fix for this is to install an LED turn signal flasher relay. The free fix is to actually modify the factory one in the truck. It's a little tedious and can be a tricky endeavor, but it 100% works; have it done on mine.
https://blazerforum.com/forum/lighti...-insane-71527/
Now if you ever install LED's into the fronts ALONG WITH LED's in the rear, even if you're flasher is modified following the method above, then you will need load resistors installed into the front signal wiring harness. With LED's all the way around, a modified flasher relay, and no load resistors, the turn signals will actually stop working completely. They'll light up solid, but will not flash. Installing a load resistor into the front harness tricks the system into seeing at least one normal incandescent bulb, and makes everything work normal again.
Now this part is EXTREMELY important...
DO NOT, I REPEAT, D O N O T , under any circumstance, install load resistors into the REAR of a Blazer or S10. These trucks use the same filament in the bulb for the turn signal and the brake light. So although it might trick the turn signal circuit into working right, it's also going to energize the load resistor when you're on the brakes. Which can be a problem when you're on the brakes for more than 10-15 seconds. Load resistors get HOT, hot enough to melt plastics, possibly start fires. That is why they come in aluminum housings with heat dissipating fins on them. When they're wired into just a turn signal circuit and only seeing power for a half a second at a time on and off, they will get warm sure, but they won't get hot per say. But when supplied with constant power (like if on the brake light circuit and holding the brakes on at a red light in traffic), they will rapidly heat up. Best case scenario, they internally burn out and cause no damage. Worse case, they set the wiring they're attached to, the taillight, possibly more, on fire... Putting them on the front though is perfectly fine. I've been running some on mine for many years now, they're resting against my plastic grill, and it's never been a problem. The front turn signal bulbs are also the running light bulbs, but you only install the load resistors into the turn signal wires, so they only see power in the half second intervals while the turn signal is flashing.
First off I'll start with my solution. It's a little more involved, but it's been flawless for several years now.
https://blazerforum.com/forum/lighti...etrofit-90983/
In regards to load resistors and LED flasher relays, here's my experience. With LED's only installed in the tail lights and no other modifications, you will get a fast flashing turn signal. The easy fix for this is to install an LED turn signal flasher relay. The free fix is to actually modify the factory one in the truck. It's a little tedious and can be a tricky endeavor, but it 100% works; have it done on mine.
https://blazerforum.com/forum/lighti...-insane-71527/
Now if you ever install LED's into the fronts ALONG WITH LED's in the rear, even if you're flasher is modified following the method above, then you will need load resistors installed into the front signal wiring harness. With LED's all the way around, a modified flasher relay, and no load resistors, the turn signals will actually stop working completely. They'll light up solid, but will not flash. Installing a load resistor into the front harness tricks the system into seeing at least one normal incandescent bulb, and makes everything work normal again.
Now this part is EXTREMELY important...
DO NOT, I REPEAT, D O N O T , under any circumstance, install load resistors into the REAR of a Blazer or S10. These trucks use the same filament in the bulb for the turn signal and the brake light. So although it might trick the turn signal circuit into working right, it's also going to energize the load resistor when you're on the brakes. Which can be a problem when you're on the brakes for more than 10-15 seconds. Load resistors get HOT, hot enough to melt plastics, possibly start fires. That is why they come in aluminum housings with heat dissipating fins on them. When they're wired into just a turn signal circuit and only seeing power for a half a second at a time on and off, they will get warm sure, but they won't get hot per say. But when supplied with constant power (like if on the brake light circuit and holding the brakes on at a red light in traffic), they will rapidly heat up. Best case scenario, they internally burn out and cause no damage. Worse case, they set the wiring they're attached to, the taillight, possibly more, on fire... Putting them on the front though is perfectly fine. I've been running some on mine for many years now, they're resting against my plastic grill, and it's never been a problem. The front turn signal bulbs are also the running light bulbs, but you only install the load resistors into the turn signal wires, so they only see power in the half second intervals while the turn signal is flashing.
Senior Member
Joined: Oct 2016
Posts: 605
From: Thomson, Ga.
Just my 2 cents, but on my current Blazer (98 LT, 2wd) I replaced the flasher relay (located behind the glove box) and installed LED bulbs on the rear only. Everything worked fine. Then over the weekend I put LED bulbs up front. Just the 3157 bulbs, not the 194s. One side didn't want to work. So I put LED 194 bulbs in and everything went back to normal. I think the case is that you have to run all LED up front. Something in the flasher relay doesn't allow for incandescent bulbs on the front circuit. And I didn't have to run any load resistors at all.
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