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Discussion Starter · #1 ·
Hey guys,

I've always loved Impalas and just recently moved to North America and found myself buying one. This forum has been a great help with understanding the car and fixing some issues I've had. So far I've had the issue where the wiring harness connected to the shifter broke, so I couldn't remove the key from the ignition, and I've also had the rear demister fail because of the harness near the interior fuse box. Both have been quick fixes based on info I found here.

I'm struggling with an issue at the moment. I want to retrofit LED bulbs in the front turn signals and the rear brake/turn lights. To prevent the hyperflash, I need load resistors. So far I've tried two different harnesses that had 3157 bulb sockets, so one end of the harness plugs into the car's bulb socket, and the other end fits into the headlight housing, with resistors in between. They both had the same issue- they work perfectly except the turn signal is not bright enough. So when the parking light is on, and you turn on the turn signal, the flashing is so dim that you can only tell it's flashing if you look very closely. So it's useless as it basically means the turn signal doesn't work at all.
Since both harnesses did the same thing, I tried just wiring a load resistor into the car's existing harness. I wired a resistor between the turn signal wire and the ground. That had the same issue, where the turn signal was not flashing bright enough to be noticeable above the constant parking light.

I'll also mention that when plugging the LED bulb straight into the car's socket, the bulb works perfectly. It's very bright when running the turn signal, and is exactly what I was looking for, except the fact that it hyper-flashes.

So I was hoping someone has some experience retrofitting LEDs and found a way around this problem? I don't want to replace the headlight and taillight housings with LED ones as that's quite a lot of money to spend simply to have LED lights. The only alternative I can think of would be a 'switchback' LED bulb which glows white for the parking light and switches to amber when the turn signal comes on, but I'd like to avoid that if possible to keep the amber parking lights.

Thanks in advance for any help or advise guys!
 

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2015 Impala Limited 9C1 馃殦
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It would help to know what year you're working with. But I'm going to assume something in the last 2-3 generations.

Skip to the bottom to just get the answer.

I'm not claiming to be an expert on cars but I do happen to have an electronics degree. You mentioned adding a resister into the harness. Was that one of those load equalizer products or just a resister you picked up? No matter what, introducing a parallel load will reduce the current available to the actual bulb. How bright an LED will be is always determined by the current it receives.

Now all that out of the way, hyperflash is a designed feature in modern cars to let you know a bulb isn't working correctly, detected as an open or short circuit. A diode gives you an approximation of both states in normal usage. So a parallel load is still needed to prevent the burned bulb detection.

The important thing is that the your new circuit needs to retain about the same impedance as original bulb. Easiest way is to check that is to bust out a multimeter set to measure resistance. 3157 should be around 30 ohms but it never hurts to check your old bulb and then the new harness with the bulb installed.

I haven't heard of the harnesses you were talking about being sold on their own. Something of that nature is built into the tail lights I installed on my car but, instead of a single bulb, that was to power an LED array with the needed electronics built into the housing. They may not be meant for the job you want used them for.

Based on what you described I do a good idea of what likely happened.

Skip to here:

Your problem and solution are simple. Your resister draws too much current so your bulb wouldn't work properly. You need to track one down that matches to the application as these are actually not universal.

Alternatively, This may be an issue with the specific bulb you used. So I can give you a straight answer, do you mind posting which bulb and resistors you used for this?
 

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Discussion Starter · #3 ·
Hi firestk,

Thanks so much for the in depth response. Sorry, I forgot to mention I have a 2008 Impala in the 50th Anniversary trim.

As for which load resistors I've used so far-

This was the first one, it had the issue of being too dim for the turn signal, but also didn't fit the headlight housing

This was the second one, it fit the housing but also had the issue of being too dim

This was the third option, where I wired one of the resistors directly between the turn signal wire and the ground.

This is the bulbs I have

Thank you for mentioning that these are not universal, as I was under the impression that they were. My understanding was that since they emulate the resistance of an incandescent bulb, that they would work for any application but I didn't realise it can actually differ from car to car. The first resistor I tried was 50 Watt 8 Ohms, and the second and third were both 50W 6 Ohm. Since I don't have a multimeter, do you have a suggestion of what values I should look for?

Thanks again
 

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2002 Chevrolet TrailBlazer LTZ 4.2L
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I pasted a link to the load resistors I used with my 2008 LT. Splice them in and you'll be good to go. One side splices into the ground wire of the harness and the other side splices in to the signal wire at the harness. Generally, the signal wire will be the brighter of the other 2 non-ground wires.

 

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2015 Impala Limited 9C1 馃殦
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I pasted a link to the load resistors I used with my 2008 LT. Splice them in and you'll be good to go. One side splices into the ground wire of the harness and the other side splices in to the signal wire at the harness. Generally, the signal wire will be the brighter of the other 2 non-ground wires.

Ok. I'm gonna propose a little experiment to test out what happened. Try taking the two resistors you have and set them up in series ( one end connected to the other) and tie that into the harness to see if you get a brighter result. If it works, you just need to get higher value resisters. No more money spent took you can see if that's the root cause.
 

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Discussion Starter · #6 ·
I pasted a link to the load resistors I used with my 2008 LT.
Thanks Mike, but from looking at these they seem to be the same as the ones I already tried, I'm not sure if there's a difference but I'll keep them in mind.

Try taking the two resistors you have and set them up in series ( one end connected to the other) and tie that into the harness to see if you get a brighter result.
So thankfully I had some time today to do this experiment, and it worked. With two of the 50W 6 Ohm resistors in series, the bulb flashed bright enough with the turn signal on. However, the car activated the hyperflash.

So when I have one resistor connected, the flash is not bright enough - and there is no hyperflash
And when I have two resistors connected, the flash IS bright enough - but there is hyperflash.

I made a video (click here) so you can see the difference in the brightness. I connected first one, then two, then three resistors in series and the flash got increasinly brighter. Note that for the video I was using the hazard lights of the car which are not subject to hyperflash regardless of the load on the circuit.

So any suggestions from here?
 

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2015 Impala Limited 9C1 馃殦
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Thanks Mike, but from looking at these they seem to be the same as the ones I already tried, I'm not sure if there's a difference but I'll keep them in mind.


So thankfully I had some time today to do this experiment, and it worked. With two of the 50W 6 Ohm resistors in series, the bulb flashed bright enough with the turn signal on. However, the car activated the hyperflash.

So when I have one resistor connected, the flash is not bright enough - and there is no hyperflash
And when I have two resistors connected, the flash IS bright enough - but there is hyperflash.

I made a video (click here) so you can see the difference in the brightness. I connected first one, then two, then three resistors in series and the flash got increasinly brighter. Note that for the video I was using the hazard lights of the car which are not subject to hyperflash regardless of the load on the circuit.

So any suggestions from here?
Ok I think we're on the right track. Between 8-9 ohms is likely be your sweet spot. Final proof for that will take 3 of those 6 ohm resistors. Set two in parallel and one in series with that to make a 9 ohm circuit then set that up in the harness. If you have 4 resistors, you can test it at 8 by adding 1 more to the parallel part of the circuit.

If it's bright enough and no hyper flash, get an 8 or 9 ohm kit (for a cleaner ,safer install) and you should have no more issues.
 

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Discussion Starter · #11 ·
So perfect timing, I just tried it five minutes ago.

I tried with two parallel then one in series, and then with three parallel and one in series, and in both cases the bulb isn鈥檛 flashing bright enough when the turn signal is active, which was the same issue with having just one resistor.

Any suggestion on where I can go from here?
 

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2015 Impala Limited 9C1 馃殦
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So perfect timing, I just tried it five minutes ago.

I tried with two parallel then one in series, and then with three parallel and one in series, and in both cases the bulb isn鈥檛 flashing bright enough when the turn signal is active, which was the same issue with having just one resistor.

Any suggestion on where I can go from here?
Looks like my estimate was wrong.

At this point, sticking with the original bulb or getting a local automotive electronics specialist to work on it is your best bet. Somewhere between 9 and 12 ohms is what you need but unless you have a ton of resisters sitting around to test it out, your just gonna be riding the struggle bus buying products that won't work until you get one that does.

If we were in the same state or at least the same country, I'd say let's make a weekend of it rig the circuit up to a potentiometer and fine tune that thing to an acceptable level of performance.
 

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2002 Chevrolet TrailBlazer LTZ 4.2L
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My post in #4 has resistors that will work for your application. I have used them personally on my 2008 LT without issue of fast flash or brightness, and am also using the same ones on my 2002 Trailblazer with similar results.
 
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