Mod to Flasher for LED's on turn Signals

[Oleksakjr]

So youll be able to run LED's in both the sidemarkers and the DRL turnsignals without the use of load resistors or anything, simply by cutting out a resistor? You said it also does not affect the DRL's... what are the issues with doing this? I think you mentioned a slightly faster flash rate than normal? I'm curious but hesitant, thanks

[CTSV_Rob]

I am busy now but I will give you the low down on this circuit after I finish work today.

[Slithering_Joe]

Originally Posted by CTSV_Rob;

....There is a comparitor circuit in the Flasher IC that compares the actual current to a setpoint determined by a .03 ohm resisitor. By taking this resistor out it disables this circuit. If you want to know how the flasher works, look up the spec sheet for a U643B and it will show you the internals of the chip and describe in more detail how the function works.

...I have done no damage and the only side effect I have noticed so far is it will no longer flash fast if a bulb does go bad. I could make the circuit work for the LED's I think but it would require changing the Flasher IC out with another designed for low power. Too much work for the option to me. If you decide you want to try to do this I could supply you with all of the chip part numbers.

Would a different resistor value enable the "bad bulb" circuit to work with LEDs?

[CTSV_Rob]

Originally Posted by Slithering_Joe

Would a different resistor value enable the "bad bulb" circuit to work with LEDs?

No, the current draw is outside the configurable range for that flasher chip (too low).

[CTSV_Rob]

Originally Posted by Oleksakjr

So youll be able to run LED's in both the sidemarkers and the DRL turnsignals without the use of load resistors or anything, simply by cutting out a resistor? You said it also does not affect the DRL's... what are the issues with doing this? I think you mentioned a slightly faster flash rate than normal? I'm curious but hesitant, thanks

I am a little disappointed with the way GM designed this circuit. They have one wire driving the DRL's and the turnsignals but they use a dual fliament socket and bulb. Since they had all of the connections they should have run an additional wire to separate the DRL from the Flasher completely.

Since they did this they decided to combine the filament they had no choice but to put the flasher and DRL together. It is a good idea to have them in the same box but I still wosh there was a second wire for the LED setup I went with.

How it works:
I am doing this from memory since it's been a while since I have worked on this circuit. If I make any mistakes and you notice them please point tem out.

There is a relay in the DRL module that switches from the Day time running lights to the turn signals. Buy disabling the DRL's what you have done is when the relay switches over to teh DRL the voltage is allowed to go through the relay and light the lamp. When the relay switches to the turn signals it then goes through that flasher chip. If you disconnect the power at teh proper point it disables the DRL (see faq) ut the turn signals will still function. Also, since the flasher is ona seperate leg on the relay, if you make the change properly then the DRL's will still work properly.

If you only do the turn signal mod then it will allow the DRL to use the LED as well as the flasher. The only down side to doing this mod is the turn signal will flash slightly faster than it did with the resistor and the incandesent bulb.

Someone on the forum made this modification and didn't care for the faster flashing. If you are on the fence about this mod then buy a spare DRL / Flasher unit from Luke and if you do not like, make the switch back to stock and it will work like it always did.

Rob

[bneal1022]

awsome info.. thanks !

[Oleksakjr]

Definitely thanks a lot

[CTSV_Rob]

If you do it, let me know what you think.

[bneal1022]

Rob,
I will have the new module on Monday evening. I was going to only do the turns signal frequency doubler, but by the way you describe it above it sounds like both mods may be the way to go. So if i understand you correctly by doing both mods with the "pin H (i think)" on the module for the DRL and cutting the flasher resistor on the board, both items will function properly yet independantly? The DRLs will come on automatically based upon ambient outdoor light, and off accordingly, and the turns will not hyper-flash as if a bulb is burnt?

Can you tell what "points" to disable each? is this the one for the DRLS?
http://cadillacfaq.com/faq/answers/disdrl/index.html

Is this the correct point for the hyper flashing - bulb out?
The beginning of this thread? Does the 0.03 ohm resistor only need seperated on one side to break the circuit, or need to be completely removed? If removed does a straight connection need made for circuit continuity minus the resistor?

Did you see my post about the "1 LED away...." I have an odd polarity issue I think that I will be unable to resolve between regarding the turns signal LEDs and and anything more than parking lights turned on. With no lights on the turns work, once the parking lights or more are turned on only the front side markers do not come on... odd. New HID fogs seem to dim the front amber DRL LEDs. Maybe it is a washout, or current draw. DRLS on only they are BRIGHT for LED, but seem dimmer once fogs are lit.

This is equally fun as frustrating..

[bneal1022]

CTSV Rob,
see my post above.. also:

I have a simple question about the circuit borad int he flasher unit. Do I remove the resistor all together, remove it from board, or simply break one side? Once removed do i need to splice across it? When you say "cut the trace" do I simply use the razor knife to cut the lead in the board? Which one I think there were 3 going to the resistor? To repair, just dab solder into the cut that I made?>

thanks
Brandon

[Slithering_Joe]

Brandon, did you see my poast about an LED for marker ?
http://www.cadillacforums.com/forums...l-led-mod.html (1 LED away from FULL LED mod AND HID - 1 wierd issue (unresolvable polarity?))

[CTSV_Rob]

Just cut the trace and it will disable the doubler circuit. I would use an exacto but any sharp blade with do the trick.

If you want to keep the DRL's do not mess with pin H.

[bneal1022]

Rob, cut any side of the resistor down into the board face to cut either lead right? fix with solder? How do I control DRL if I trim pin H. They just stay off but only come on as turns? Never DRL again?

Slither.. I got your message, thanks. Makes sense. I found that ALL lights will work properly (excluding hyper-flash) if I just leave the rear turns as regular bulbs. So I guess that i can't complain with EVERY other interior and exterior buld now being LED.

You guys rock.. I will post pics once I have car back together and outside... A super nice guy in TX did my clear fogs for like $50 including shipping. found him on ebay.

[CTSV_Rob]

Cut the trace on the Chip side or the right side of the resistor as pictured in the first post. You need to cut all the way through the trace to make sure it is no longer connected. There is no need to solder it unless you want to undo the mod.

What are you trying to do with the DRL?

If you want to disable then trim pin H, if you want to leave the DRL's on then do not touch pin H.

[bneal1022]

Rob..

Look at the pic. I drew a line in yellow. Please confirm this is the trace I should cut. Thanks.

Not really wanting to do anything with my DRL, I suppose that disableing them mean theys simply do not come on anymore only as turn signals right?