Mod to Flasher for LED's on turn Signals

[CTSV_Rob]

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/answe...drl/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.

[Lindsay Cadillac Parts]

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[nikon]

good deal...I'm sure the cts guys will be all over this....FAQ material!

[atdeneve]

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.

[WheelHop]

Um, ok. Cool.

[CTSV_Rob]

Originally Posted by atdeneve

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.

[atdeneve]

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?

[nikon]

^^^ de-solder it....pretty easy.

[CTSV_Rob]

Originally Posted by atdeneve

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.

[Ak Jim]

Rob, how did you figure this stuff out? Are you an EE?

[CTSV_Rob]

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.

[bneal1022]

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.

[CTSV_Rob]

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.

[bneal1022]

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.

[CTSV_Rob]

same board, It controls the flasher and the DRL's.

Let me know if you have any problems with it.