Cadillac Owners Forum banner

1 - 20 of 57 Posts

·
Registered
2007 CTS-V Thunder Gray; 2004 Cowboy Cadillac (SRT10)
Joined
·
17,712 Posts
Discussion Starter #1
I wanted to replace the bulbs with LED's but I did not want to put an additional load on the circuit. I did a little investigation and realized the DRL was part of the flash module so the module could not be replaced with an off the shelf unit easily.

I used CadillacFaq to find the module and eliminate the DRL's

http://www.cadillacfaq.com/faq/answers/disdrl/index.html

Then while I had the module out I figured out how to disable the frequency doubler to indicate the incandescent bulbs need to be replaced. To do this a resisitor needs to be removed and this will disable the doubling feature. The only down side to this is it will no longer blink faster if the bulb goes bad (I can live with this).

If you decide you want to do this mod then all you need to do is to remove the resisitor circled in the picture below.
 

Attachments

·
Registered
Joined
·
2,114 Posts
I don't quite follow. Where does this all fit in to switching to LEDs? Why is it required to disable the flasher frequency doubling?

Oh, wait, nevermind. Guessing that if you put in LEDs, the lower resistance across the LEDs allows for more flow, thereby causing the flasher to double in frequency. Yes? No? Someone wanna explain.
 

·
Registered
2007 CTS-V Thunder Gray; 2004 Cowboy Cadillac (SRT10)
Joined
·
17,712 Posts
Discussion Starter #6
I don't quite follow. Where does this all fit in to switching to LEDs? Why is it required to disable the flasher frequency doubling?

Oh, wait, nevermind. Guessing that if you put in LEDs, the lower resistance across the LEDs allows for more flow, thereby causing the flasher to double in frequency. Yes? No? Someone wanna explain.
You are correct, The LED's draw less current and the Circuit "thinks" the bulb has gone bad. The modification eliminates this check so you can run lower current bulbs or LED's and the flasher will still work normally.

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 changed over to the clear lenses and did not want an orange bulb, thought it would be a bit ugly. The LED was a cool option because when it was off the LED is clear and when on it's a pretty intense orange. Don't need to be ricer to appreciate newer technology.

I didn't like the orange when I was a kid riding BMX (the reflectors on the wheels) and I still don't.
 

·
Registered
Joined
·
2,114 Posts
Cool. So we can just yank the resistor and have no mal/side-effects. How do we yank said resistor, without doing any damage? Just carefully pry it off?
 

·
Registered
2007 CTS-V Thunder Gray; 2004 Cowboy Cadillac (SRT10)
Joined
·
17,712 Posts
Discussion Starter #9
Cool. So we can just yank the resistor and have no mal/side-effects. How do we yank said resistor, without doing any damage? Just carefully pry it off?
You could either use the tool that tomm listed in his "Replace the orange LED's" thread but that unit cost about $500 so too much for me.

I used Solder Wick and a soldering iron. The solder wick is nothing more then a thin copper braid and when you put it in between the soldering iron and the solder joint it "sucks" up the solder into the solder wick.

Another option is to take a sharp exacto knife and cut the trace next to the resistor. In hind sight this is the way I should have done it because you could restore the circuit by just repairing the trace.

I will be writing instructions on how to modify the board and I will give to CTSVett to post on the Faq.

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.
 

·
Registered
2007 CTS-V Thunder Gray; 2004 Cowboy Cadillac (SRT10)
Joined
·
17,712 Posts
Discussion Starter #11
Customer Service Engineer on Semi conductor equipment but basically a jack of all trades. Being in Customer Service we need to modify circuits and hardware to make them function as the customer would want it (me in this case). Makes sense I can't keep my fingers out of the V now doesn't it. :thumbsup:
 

·
Registered
2005 CTS-V, K&N, Borla, short throw w/ Holden knob, hotchkis
Joined
·
906 Posts
Do you have to effect the function of the DRL to eliminate the doubling of the blinker by removing the resistor? I do not really want to have an adverse effect on the DRL but want the benefits of lower draw and no fast blinking.
 

·
Registered
2007 CTS-V Thunder Gray; 2004 Cowboy Cadillac (SRT10)
Joined
·
17,712 Posts
Discussion Starter #13
Completely separate. I did the DRL mod too but you can do both of these mods independant of each other.

Warning: By removing this resistor it does blink a little faster than it did before. The savings in current draw on the system was well worth it to me.

Do not remove the resistor, just take an exacto and cut the trace next to it. This way if you decide you do not like then you can put it back and no harm, no foul.
 

·
Registered
2005 CTS-V, K&N, Borla, short throw w/ Holden knob, hotchkis
Joined
·
906 Posts
heck yeah.. thanks ! So is it the same board. I saw your photo above and the board is green but if you search "flasher" there is a FAQ that shows removing a pin to disable the DRLS (glad it is seperate). Is that the same board? green / beige? I ordered a seperate module in the event I goof.
 

·
Registered
05 CTS-V & 06 Rubicon
Joined
·
365 Posts
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
 

·
Registered
'05 CTS-V, Powered by Chevrolet
Joined
·
835 Posts
CTSV_Rob; said:
....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?
 

·
Registered
2007 CTS-V Thunder Gray; 2004 Cowboy Cadillac (SRT10)
Joined
·
17,712 Posts
Discussion Starter #20
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
 
1 - 20 of 57 Posts
Top