Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner

LED Flasher Relay

161K views 104 replies 39 participants last post by  ch7 
#1 · (Edited)
Hey guys, I'm new to this site but was a member of an Explorer Forum for about 3 years so I am familiar with how these work. The Explorer was sent to the junker for the cash for clunkers program and I was awarded with my mom's 2004 Envoy.

I have already converted the front low beams and fog lights to HID (6000k lows and 5000k fogs). I have done a full interior LED conversion and changed out the bulbs in the reverse lights and license plate lights to LED. I am looking to take the next step with blinker bulbs and brake bulbs.

I am familiar with doing LED taillight bulbs because I changed them out on my old Explorer and used load resistors to get them to flash normally. I wanted to find an easier fix for this though rather than tapping into a bunch of wires.

I have taken some pics of the blinker relay. It is a GM 12450284 relay that is used on most GM trucks. It operates the blinkers on the truck and for the trailer lights (when using). I've included pics of where the relay is located and how to remove it. Use a flathead screwdriver to push the small tab down and slide the clips to the larger holes. It should slide out the whole thing. Then push back the grey clip to loosen the hold on the relay. You may need to use a flathead to pry out the relay too. Be careful not to damage it. Here are the pics and now for the good news.













I have found a solution to the relay. I have found a product online called named GM LM455. It is the same 10 pin relay except with the right load for LED bulbs or a mixture of LED and incandescent bulbs. I am ordering one and will see what the outcome is. Here is a pic.

New Relay:
 
See less See more
7
#5 ·
I got the LM 487 (Napa) and it works perfectly for all my LEDs EXCEPT the tail running lights (the ones that come on at night). I don't know why, but everything works fine, including cruise control and the brake lights, but the tails just don't come one when the headlights do. Are you having the same problem?
 
#6 ·
Mine just came in the mail today and I have to say I'm disappointed.

It clearly says "LED" on the front, but I still have a hyperflash issue. I pulled the relay apart and compared it to the OEM relay and they have almost identical inside parts except one piece (which I don't believe makes a difference but I could be wrong).







Clearly says LED but definitely no improvements with the flasher. A little upset.

How much was the LM 487 and where was it purchased? Do you have LEDs at all corners?
 
#8 ·
Alright because my new relay says LED on the front and has hyperflash, but I do have LEDs in the front and the back. I just wonder if that's why I'm having the problem.
 
#10 ·
Thanks for the help man. After doing a bit of research I found the LM487, then I came back here and saw you had the same reply. I'll be taking a trip out tomorrow to a NAPA to get the flasher I need. Thanks a bunch :hail:
 
#12 ·
It is confirmed. The LED flasher relay is the LM487 from either Napa Auto Parts or from LEDlight.com (http://www.ledlight.com/electronic-led-flasher-lm487.aspx).

I just put it in and had a nice drive so I tested out cruise control, which has gotten criticism for not working with this flasher. Functioned fine and the flash is finally normal as well. I believe this flasher is electronic and I was worried about it not clicking with my turn signals but it still clicks a relay, which is good.

If you have LED signals and don't want to get a million load resistors, this is the easiest fix.

Benjamin, I haven't ridden with the relay at night yet but I will let you know if I have any issues.
 
#13 · (Edited)
So what's happening is my RR park (#17) and LR park (#14) fuses are blowing when my lights turn on, disabling the parking lights. Tried with and without resistors. Are you having the same prob?

For now I'm just going to put my old filament bulbs back into the park/brake sockets so I don't get pulled over for no parking lights or license lights.
 
#19 ·
No not every bulb. It might even work with incandescent bulbs. I know a mixture is fine because I'm pretty sure it's electronic, so it doesn't rely on the load of the bulbs.
 
#21 · (Edited)
No problem. I have the link up there^ if you want to order it online for 20 fewer bucks than from Napa. But, I had never used Napa before this and I was happy with the level of quality and the service I got. I called and they didn't have it in stock but got it there by the next morning. Great service.
 
#24 ·
Received the LM487 this morning. Installed it in place of the original flasher. Installed two Amber 27 SMD LED 3157, and two Amber 5 SMD LED 194 in the Headlamps, two Amber 5 SMD LED 194 in the mirrors, and two Amber 27 SMD LED 3157 in the tails. Flashing speed was normal. All functions worked perfectly.

Here are some pictorial comparisons of the LM487 and the 12450284.

Internal comparison of the two
Technology Electronic device Electronic component Electronics accessory Electronics

Internal of the 12450284
Circuit component Electronics Technology Electronic component Passive circuit component

Internal of the LM487
Electronics Hardware programmer Technology Sensor Electronic device

What's under the LM487 Sticker
Technology Electronic device Electronics Passive circuit component Circuit component

Yes that is a legitimate GM Part Number. It may or may not have been modified. Anyway GMpartsdirect wants more for it than ledlights for the LM487. And it does work correctly with all LEDs.:thumbsup:

:eek:fftopic:I also installed two White 27 SMD LED 3157 bulbs in the cornering lights and two White 27 SMD LED 3157 bulbs in the Backup lights. What a difference in the color and brightness. WOW!:excited:
 
#27 · (Edited)
Well this may be my next thing to get because I have all my bulbs to LEDS and put load resistors at the front main signals and now one of the connections doesnt hold well...

Also noticed that when my lights are off when I use the right signal the left side blinks dim as well as the back left BRAKE light :weird: and vice versa for the other side... (I have the IPCW Bermuda tails)

but it works normally when the lights are on

funny that I just noticed that issue today :(
 
#28 ·
That's a little strange. This would definitely be the easiest fix.

Also, an update on my flasher; I go to LSU and came to GA this weekend for the game. On the way here, when I needed cruise control the most, it decided not to work, even though it worked when I first got it. I thought about popping out the electric flasher and putting in the OEM one just for the car ride to get that cruise control working. The cruise has worked before but didn't yesterday so I guess it can be a bit faulty with this relay.

Still, I believe that one tiny fault with a normal flash is something I can exchange. I'm sure most of you would agree.
 
#29 ·
I have to point out a few things.

The flasher is also made by Grote part number 44140 (i'm a dealer).

You can use the flasher to control the front (turn signal) OR rear turn signals.

You cannot use the LED flasher to control (4) corners. I did extensive testing with these led flashers include GM parts too--I'll look up the part numbers and edit the post.

You will lose cruise control ONLY if you switch your BRAKE lights to LEDs AND use the LED flasher module.

example: you have switchbacks in the front....the LED flasher module...and stock halogen bulbs...your cruise will work just fine.

If you replace your brake/parking lights (trailblazer)..you will lose cruise.
----

Lastly, I also figured out that you can use LEDs in all 4 corners of the truck using only (2) Load resistors. I didn't want to cut/splice any wires. But for $9.00 and a quick tap..and run the other wire to body ground, it's been working great for my personal truck, and if you don't know I have 100% LED conversion.

I hope that helps a few guys out.

-Mike
 
#33 ·
I sorta have to disagree with you:no:. At least in the case of my Envoy. I am running four Amber 27 SMD 3157 in the turns, two Amber 5 SMD 194 in the front turns, two Amber 5 SMD 194 in the mirror turns, four 20 Superflux 3157 dual ckt. in the tail/stop that were converted to quad stop, and an LM487 flasher. I have no load resistors, normal flashing speed, bright brakes, And have no problem with my Cruise Control. I am no expert but I would think if there was an issue with the Cruise Control that resistors would be needed in the brake ckt. I did notice on the Stop Lamp schematic the flasher socket pin B has a signal from the stop lamp switch. So who knows:undecided. Certainly not me:bonk:.
 
#41 ·
I have some new news about the cruise control issue.

I hadn't tried using my cruise in a while but after I had installed my remote starter with an INT-SL module, it started working again. I'm not sure if it has something to do with the module interfacing with the car or just total coincidence but the cruise works now and has worked for weeks.

The whole cruise control thing continues to baffle me, but at least for now, it is operational.
 
#42 ·
I wander if that could be the reason I never lost the the operation of my cruise control? I have had an after market DEI Avital alarm and remote start on my truck for some time now.
 
#44 ·
After reading this WHOLE thread I am now debating on converting all bulbs to LED and getting the LM 487 and possibly running into more issues with my cruise control. Does anyone know for sure on the Trailblazer? I do not want to risk loosing my Cruise control, especially if I spend all this money on LED Bulbs.
 
#45 ·
As stated before, it seems to be a pretty unpredictable thing. Mine works all the time now but I did go through a period where it wouldn't activate. I don't know if anyone can guarantee anything.
 
#49 ·
LED's

I have a 2007 Trailblazer and I have all LEDS for it... I have them currently in the stop lights, the SMALL 194 corner turns, backups,licenseplate, all interior... The stop lights have the little resistor built into it as well as the ones for the front and rear turns.. I installed them and got the hyper flash even though they have a built in resistor... IF I was to get the LM 487 flasher, will that fix the problem and my Cruise still work too??
 
#50 ·
I have a 2007 Trailblazer and I have all LEDS for it... I have them currently in the stop lights, the SMALL 194 corner turns, backups,licenseplate, all interior... The stop lights have the little resistor built into it as well as the ones for the front and rear turns.. I installed them and got the hyper flash even though they have a built in resistor... IF I was to get the LM 487 flasher, will that fix the problem and my Cruise still work too??
Honestly bro, order the resistors for the rear turn signals from jetttstream.com and call it done. Tie them into the rear turnsignals ground and trigger wire into the harness and you will be good. BE sure you ordered the right taillight(rear) and front turn signal bulbs for the truck. The traditional 3157 LED bulb off any website will not cut it. I ordered the rear bulb from jetttstream and mike helped me understand the whole process. And I still have my factory turn signal flasher in the truck. PM me if you have anymore questions.
 
#55 · (Edited)
I FINALLY GOT IT FIGURED OUT!! LM 487 and 400 ohm resistor:woot:

The 5vdc(lights out) and the 7vdc(lights on) on the brake circuit is not LED related feedback, it's from the monitoring circuit for the cruise disable input. The LM 487 was not designed for single brake light assemblies, but for the full size trucks, with the quad brake lights. This is probably why most of you with quad brakes have less problems with the cruise and the LM 487. I have soldered a 400 ohm, 1/2 watt (it's 1/8"W x 5/16" L) resistor on the LM 487 between the brake terminal(B) and the ground(E). This dissipates the small amount of voltage from the cruise cutout circuit, and allows the cruise control to work, for those of us who don't have quad brakes. It also still disengages the cruise control when the brakes are applied. No need for load resistors on the signal lights, and I still have full brake output, in case anyone was concerned about that.

This post should take of all the questions previous in this thread. Glad to help.:woohoo:

_________
Belltech 2/3; SP shocks/struts; Susp Maxx end links; LEDs: rr turn & mirror, brake, license, reverse; LED relay mod
 
  • Like
Reactions: VI_Bonvoy
#56 ·
I FINALLY GOT IT FIGURED OUT!! LM 487 and 400 ohm resistor:woot:

The 5vdc(lights out) and the 7vdc(lights on) on the brake circuit is not LED related feedback, it's from the monitoring circuit for the cruise disable input. The LM 487 was not designed for single brake light assemblies, but for the full size trucks, with the quad brake lights. This is probably why most of you with quad brakes have less problems with the cruise and the LM 487. I have soldered a 400 ohm, 1/2 watt (or maybe 1/4 watt; it's 1/8"W x 5/16" L) resistor on the LM 487 between the brake terminal(B) and the ground(E). This dissipates the small amount of voltage from the cruise cutout circuit, and allows the cruise control to work, for those of us who don't have quad brakes. It also still disengages the cruise control when the brakes are applied. No need for load resistors on the signal lights, and I still have full brake output, in case anyone was concerned about that.

This post should take of all the questions previous in this thread. Glad to help.:woohoo:

_________
Belltech 2/3; SP shocks/struts; Susp Maxx end links; LEDs: rr turn & mirror, brake, license, reverse; LED relay mod
Wow, excellent research man. I would have never been able to figure it out or thought of where to begin testing.

Much appreciation for your hard work and research :thumbsup::thumbsup::thumbsup::thumbsup:
 
#57 · (Edited)
Simple Fix for Hyper flashing

Long story, Re-wire to put in Quad REd LED Brake light and 2 LED Amber Turn Signal, Hyper flashing on Turn signal. Find and read this thread. Put in part# LM487 from NAPA, everything work fine except my remote car starter.

Take a while to figure out.

Thanks to doorman post on page 6 of this thread. Find out the LM487 have 4v on the brake line ( terminal B ) on the new Flasher relay. THat why my Remote start won't work, because it sense the Brake is on. (That will make the Cruise control not working as well ).

Take apart my old GM OEM Flasher, part# 12450284. Find out they use U643B Flasher IC. Download spec for the IC. Figure out how the chip works.

Do some math, here what I have to do, If you have a solder iron:
(Pictures of the module on Page 3 of this thread)

- If only replacing rear TURN SIGNAL to LED
Replace the Metal strip on the old Flasher module to .10 ohm 5W resistor.
Be careful make sure the legs from the Resistor not touching any other metal parts in the module.
DO NOT JUST CUT THE STRIP, have to remove it out the the board.

- If you are replacing ALL TURN SIGNAL to LED
Replace the Metal strip on the old Flasher Module to .15 ohm 5W resistor.
Be careful make sure the legs from the Resistor not touching any other metal parts in the module.
DO NOT JUST CUT THE STRIP, have to remove it out the the board.

Right now, I'm using the old module with the .10 ohm 5W resistor, everything works. Turn signal flash normal. Remote starter works, Cruise control works.

I will post again if there are any new problem show up.

:):):)
 
#67 ·
Long story, Re-wire to put in Quad REd LED Brake light and 2 LED Amber Turn Signal, Hyper flashing on Turn signal. Find and read this thread. Put in part# LM487 from NAPA, everything work fine except my remote car starter.

Take a while to figure out.

Thanks to doorman post on page 6 of this thread. Find out the LM487 have 4v on the brake line ( terminal B ) on the new Flasher relay. THat why my Remote start won't work, because it sense the Brake is on. (That will make the Cruise control not working as well ).

Take apart my old GM OEM Flasher, part# 12450284. Find out they use U643B Flasher IC. Download spec for the IC. Figure out how the chip works.

Do some math, here what I have to do, If you have a solder iron:
(Pictures of the module on Page 3 of this thread)

- If only replacing rear TURN SIGNAL to LED
Replace the Metal strip on the old Flasher module to .10 ohm 5W resistor.
Be careful make sure the legs from the Resistor not touching any other metal parts in the module.
DO NOT JUST CUT THE STRIP, have to remove it out the the board.

- If you are replacing ALL TURN SIGNAL to LED
Replace the Metal strip on the old Flasher Module to .15 ohm 5W resistor.
Be careful make sure the legs from the Resistor not touching any other metal parts in the module.
DO NOT JUST CUT THE STRIP, have to remove it out the the board.

Right now, I'm using the old module with the .10 ohm 5W resistor, everything works. Turn signal flash normal. Remote starter works, Cruise control works.

I will post again if there are any new problem show up.

:):):)

I was told I needed a .15 Ohm 5W resistor to stop my hyper flashing when I have my T/S on and brakes applied with 100% LEDs. I cannot find a .15 ohm 5W resistor just a 15 Ohm 5w
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top