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Odd thing....passenger side (dim) headlamp has dangling

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Odd thing....passenger side (dim)...

Odd thing....passenger side (dim) headlamp has dangling black wire (leading from the lamp clip-on). Attaching it to any ground or the main ground (black) completes the circuit and the light stays on...won't turn off.

Mechanic's Assistant: Just to clarify, what are the exact lights you're talking about?

2005 Impala....passenger side (dim) headlamp...

Mechanic's Assistant: Are you fixing your Impala yourself? What have you tried so far?

Yes. I have wired the dangling black to the "main" black to ground it and have also "completed" the circuit by just touching the dangling black wire to metal. The head lamp stays on (with or without starting the car)

Submitted: 3 months ago.Category: Chevy
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Answered in 9 hours by:
4/4/2018
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago
Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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The ground side of the RS headlight should be a dark blue wire, are you sure this wire is black, and not dark blue?

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Customer reply replied 3 months ago
What is "RS"? And it is most definitely black. And now having additional odd lighting problems....my opinion is a bad circuit/switch, as power must be passing through a switch prior to the light....I've ordered a multifunction switch as my (now) multiple problems suggest that's at least 1 of 2 possible issues.
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

RS = right side. Sorry about my shorthand.

Lights on this car are controlled by the body control module, and it controls them on the ground side. They have power at all times, which is why the light stays on when you ground this wire. This wire should be attached to a connector, which leads into a harness and ultimately ends up at the BCM under the dash.

BCM's are notoriously faulty, if you have weird lighting issue, it's probably more to do with the BCM and less so with the multifunction switch, which is nothing more than an input to the BCM.

Please take a moment to rate my answers by clicking on the stars at the top of the page, that's how I get compensated. Let me know if you need anything else.

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Customer reply replied 3 months ago
I kind of thot RS meant right side...you have answered my puzzle about constant power anyway...I may get creative and just wire in my own on - off switch if the multi fx switch doesn't solve things...it arrives Friday...( got a cheap one) will install Sunday...and see if my other problems clear up too...will get back to you Sunday afternoon...
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

OK, look forward to it.

Please take a moment to rate my answers by clicking on the stars at the top of the page, that's how I get compensated. Let me know if you need anything else.

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Customer reply replied 3 months ago
Will,rate when we complete...that ok?
Customer reply replied 3 months ago
Oh...any thots on why just the passenger side stays on but not the driver side?
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

That's OK.

Each headlight has its own circuit, they are not wired in parallel, so the ground for the right side headlight has nothing to do with the left side headlight.

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Customer reply replied 3 months ago
Thanks...makes sense now.
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

:-)

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Customer reply replied 3 months ago
It occurs to me that I have a couple days before I get the switch I ordered, so meantime, let's assume a new switch won't solve my headlight issue. Where would you point me to look for the problem?
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

The body control module. Like I mentioned before, it actually controls all of the lights in the car, and we have lots of problems with BCM's in these cars, they have been trouble since these cars were new.

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Customer reply replied 3 months ago
replace it? isn't there an alternative "fix"...and doesn't the BCM then need programming?
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

No, I wouldn't recommend just replacing it. It's where I'd be looking for issues, though, with a scan tool. The mechanic can see inputs and outputs, command lights on and off to verify that the circuits work, etc. and can determine whether the BCM is good or not. And yes, if it needs replacement, it must be programmed using dealer-level equipment, so the reality is that if you think that's the direction it's going, that would be the time to get it to your mechanic and have him do all of the above and see if the BCM is the issue.

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Customer reply replied 3 months ago
OK. I'll wait for/install my switch, then see if the other issues get corrected, then proceed.
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

That's a good plan!

:-)

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Customer reply replied 3 months ago
More thinking on my part....I've not found a schematic online...I'm trying to grasp the logic of the power circuit. If I understand you correctly, power is always "on" at least in the headlamp circuit, and is shut "off" by the BCM, which cuts the ground (how is a mystery as I think in terms of switches for off/on). As the ground isn't be set to "off" by the BCM, then that's the issue. Do I have it figured? And if so, then that means that the "manual" headlight switch as well as the automatic on when started are just signaling the BCM to complete the ground...not really turning on /supplying "hot" power. Am I getting it right?
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

You are correct. A switch is a switch, doesn't matter if it's on the positive side or negative side of a circuit. Works the same either way.

GM typically wires computer controlled circuits so they're controlled on the ground side. Just makes it easier for them, in terms of wiring, I suspect. Headlight switch is simply an input to the BCM, BCM grounds the headlight circuit to make the light come on.

You are manually grounding that circuit, and the light comes on and stays on, as it should. But if that wire were attached to the control unit like it should be, the ground would be controlled by the BCM, and thusly so would lamp control.

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Customer reply replied 3 months ago
Is it possible that one of those "ground the circuit" signals sent to the BCM by the manual or automatic after start circuits is in a continuous "send" status due a malfunction in one of those switches (the ignition/start or the manual pull/out)?
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

It is possible, but the wire is not connected at this point, or at least last I heard. We don't know if it's grounded or not, do we?

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Customer reply replied 3 months ago
I am just puzzling things out....and after I get my switch from Amazon installed (due later today) then I will re attach the black ground in the headlamp, and see what happens.
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Let me know how it turns out.

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Customer reply replied 3 months ago
Back to square 1. The replacement switch failed totally...not one function worked once installed. It was not a matter of connections as they fit together one-way only by design...all 3 of them. Wasn't fuses getting blown either, as once I re installed the original switch everything worked as it should. I'm returning it to Amazon of course.
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

That is unfortunate.

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Customer reply replied 3 months ago
I am annoyed on 2 counts. First, I can not find a schematic online that has the same colors as my car's headlight system. And 2nd, I saw so much corrosion in the connecters body-to-head lights I decided to make my own (as new ones are pricey, even generics that can be adapted) Thinking the corrosion contributed to my problem I disassembled the connectors but failed to make a complete diagram...so now I am in a fix...I can get each to work...bright, dim, amber running, but NOT as they are supposed to. Do you have access to a schematic?
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

I do, you just need a headlamp schematic?

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Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

See attached, does that match what you have there?

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Customer reply replied 3 months ago
This is closer than anything I've found...has all the right colors except yellow..I'll see what I can do. thank you.
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

You're welcome!

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Customer reply replied 3 months ago
The schematic provided doesn't have a couple colors I have so, can't sort it out. I have made "progress" of a sort. I get an all on or none on response with my current connections. All on from the manual / pull out headlight switch. A nothing on w/o it, even when the engine is running. I'm quitting for today. It's discouraging because I have matched colors headlight side to car side using the original connectors, but the above is the result. GRRRRR!!!
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

This isn't a former police cruiser, is it?

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Customer reply replied 3 months ago
Don't know that it is...doubt it....my daughter calls it a "gangsta" car ...because of the dark windows, slight rear elevation, and mags. :-)
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

I ask because cruisers have different lighting schematics. If you give me the VIN I can look it up and see.

:-)

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Customer reply replied 3 months ago
I'm at work right now....will send it tomorrow.
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

OK.

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Customer reply replied 3 months ago
VIN: 2G1WF52E059200509 Also, it just occurred to me to look at /compare the driver side headlight wiring to see if it's a duplicate...and then find my error. Any reason that wouldn't work?
Customer reply replied 3 months ago
OK...here's where we are. I pulled the connections from the opposite/driver side and duplicated what was there for the passenger side connections...Everything works as it should EXCEPT the passenger side BRIGHT. I'm going to live with that as this clearly is a very perverse electrical system. By the way, I tested the (bright) bulb, the one that doesn't "on"...it works.
So unless you stumble upon a genius idea...I think I'm done. I'll rate and pay after you respond to this.
Customer reply replied 3 months ago
I'm thinking you have been on a weekend. Were you able to locate a schematic? My lights work as described above, but I'd like to correct the one remaining issue.
Thanks.
Royce
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