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Discussion Starter · #1 ·
First, I apologize if this has already been asked many times, but the only thing I found was threads about disabling DRLs. I'm trying to replace the high beam headlights with LEDs. I bought a set of 9005 LEDs off of eBay, and they are actually quite bright and focus very well. Problem is, during the day, the DRLs don't work and it automatically switches on the low beams and interior lights, like it thinks it's nighttime. I've read that the DRLs work by running the high beams in series, and sure enough, I'm only getting 6V when the DRLs are on (with standard halogen). I already tried those $10 "DRL decoders" from eBay and it didn't do anything. What if a large resistor in parallel to simulate the load of a halogen lamp was used? Then there'd have to be some way to boost the 6V to 12V. Is there any way to fix this? I don't want to go to HIDs. For now I switched back to halogens, but I'd like for this to work.
 

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I have LED high beams and I installed a load resistor in the high beam side. My DRLs don't work but I don't have a "highbeam out" message. The load resistors I got just plugged right in to the 9005 connector; no splicing or cutting wires.
 

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My impala is an 04 and it has some canbus that says when certain bulbs are out. Yours may not have that, IDK.
The LEDs draw so little current the BCM thinks they are burned out so it turns on low beams because it wants DRLs.
I got these LEDs:
http://s.aliexpress.com/emIR7BNV
They are ok, and with the quad headlight mod it's nice, but I'll go to HID eventually.
 

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I always had this same problem trying to use LEDs as the DRL/highbeam lights. I would always get a "highbeam out" message and it would cut over to the low beams, like you describe. Even a load resistor wouldn't help.

I also have the quad headlight mod (turns headlights back on with highbeams), however, that is also causing me issues with the DRL. The low beams come on with the DRL, and with the low beams being HID and the DRL being halogen, it looks really strange. For a while I could flick the high beams, and it would trigger it so that just the DRL lights would stay on, but that trick doesn't work anymore. I've taken to just turning on my headlights all the time, which isn't ideal.

All of that to say, the DRL system on these cars is a major PITA that is a hinderance to modifications of any kind.
 

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Discussion Starter · #6 ·
Yeah, I'm beginning to hate DRL.... What's weird is the first time I put the bulbs in, the DRL system acted somewhat normal. No light on dash, low beams did not come on. The LEDs came on for a second, then the driver side was really dim (could hardly see it was glowing for any further than 2 feet away) and the passenger one was off completely. Then I swapped one bulb back to halogen and that's when it started switching on the low beams. So, I think adding a resistor might help in my case, but I don't know. I've noticed there is a difference in some of the wiring between the 2000 and 01-05 Impalas, so maybe I'll luck out on that part and the BCM will be happy with it. I was thinking, if I can get it to keep the DRLs on, would something like this work?

DC-DC 100W 3-35V 12V to 3.5-35V Boost Step-up Power Supply LED Voltmeter N144 | eBay

If I wired this between the LED driver and the headlight (for each one), at 6V it'll put out 12V and at 12V it'll put out 18V. The LED drivers are rated for 12V to 24V. My only concern would be blowing a fuse or the 18V getting back through the rest of the electrical system somehow. I guess I wouldn't be out much to buy one and bench test it and if it doesn't draw too much current or burst into flames, put it in the car and see what happens.
 

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That may work, but now your brights will be on at all times. Is that something you want?
 

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Rather, on high beam when DRL is on.
 

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Discussion Starter · #9 ·
Yeah, that's what I'm hoping to do. The only two issues I could think of would be the lifespan and being too bright for oncoming traffic. I stood back from the car and they don't have an annoying glare during the day and since at night the automatic headlights will come on, it should be ok on that. On the life span they didn't cost very much, so replacements would be cheap. I ordered the resistor and voltage regulator. I'll post an update with whether it works or not. Hope I'll get it by the end of next week.
 

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Discussion Starter · #10 · (Edited)
Well, the voltage regulators came today. I have not received the load resistors, but I won't need them anyway. The current is now 4.5 amps per bulb, which is more than the factory bulbs draw. So, I replaced the passenger side bulb with the voltage regulator, then plugged the LED driver into the voltage regulator and the bulb into the driver. High beams worked as normal. (One fully lit up halogen, one fully lit up LED). Regulator was a 13.2V. Now, with key on, engine off, I put it in reverse. The LED came on full brightness, but flickered on and off repeatedly for a few seconds, then went back to turning on the low beams. Also could hear a relay clicking on and off rapidly as well. Working on a new idea here:

I've heard if you remove pin 87 (or is it 87a?) from the DRL, you can disable the DRL without causing problems. What if I used pin 87(87a?) to trigger another relay which goes directly to the highbeams and use a diode to prevent the 12V from the battery frying the BCM? Here's a drawing of the circuit:
http://oi64.tinypic.com/2uoggfm.jpg

Update: Re-read what I read. Cutting pin 87 DIDN'T work...
Update #2 : I had a spare relay and bent in 87, and got "Highbeam Out". Complete removal of relay changes that to "SERVICE VEHICLE SOON". Guess there isn't much else I can try. I guess I'll be keeping the halogens.
 
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