The plastic taillight assemblies on my 2013 Buick Regal melted around the brake light bulbs. The car has 65,000 miles on it. A mechanic advised me to replace the taillight assemblies, which I did with used OEM parts (parts are no longer available from Buick). It's been less than 500 miles, and these are burning the plastic around the brake light bulbs, too. The bulbs are the correct ones. Several mechanics have checked the plug-in connectors coming from the car and said they are working properly. So, why is the plastic melting? The car was rearended and repaired five years ago, but the company claims they only replaced the taillight assemblies; that no wiring was done. Please advise. I've already spent $500 and still have melting taillights.
Excessive heat in a circuit is caused by either a poor connection (arcing) or high resistance (corrosion).
Either way I'd say it's time for new tail light harnesses.
But first, since the car was rear-ended maybe check the Ground Point G401 to make sure it isn't rusted or corroded.
Then check the resistance in the Black (Ground) wire between the Brake light sockets and Ground Point G401
Ground Point G401:
Thanks for the response! But the wiring harnesses were replaced as part of the taillight assemblies. They were used parts, but all four of them (two on each side) burned out. I thought it must be coming from the wiring connector plug coming from the car, but several mechanics said the ones on both sides are working properly. Could it be because they're checking it while the car is in park, and not when the brakes are being used? Could there be a short or some other issue that's not showing up except while driving?
OK. That's a useful addendum to your top post which stated: but the company claims they only replaced the taillight assemblies; that no wiring was done
.
But not your fault. These "back and forth" conversations are helpful in "drilling down" to what's going on
.
Have your guy do a voltage drop test between the battery Negative post and Ground Point G401
.
If that's OK then do the same by back probing the Brake Light Ground terminals and Ground Point G401 (brake lights on)
.
Now you've replaced those wiring harnesses with used ones
.
You probably would have been better off buying aftermarket new
.
The tail light assemblies don't matter when it comes to the electrical circuits. They're just plastic and none of the 4 bulbs use any part of them for Power or Ground. Each socket has its own Power and Ground wires
.
So I use Lunapic.com to highlight wiring diagrams and their site was down last night so I couldn't do it. I require a simple interface, I do cars, not photo editing
.
Their website is up again so I can highlight and circle some stuff in the diagram
.
Here we can see that the Power to the Brake Lights and Turn signals are provided by the BCM (I highlighted it in Red)
.
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Notice there isn't a fuse in the Power side of the circuit. That's because the BCM monitors for voltage draw. Any "Open" or "Short to Ground" and the BCM will shut down the circuit. But that isn't happening
.
Also, look at the symbol I circled in Purple in the wiring diagram. What the heck are those? They look like partial Zener Diode symbols but their placement in the circuit makes no sense
.
Typical Zener Diode symbol:
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So maybe either @imperator or some other forum guys who have better knowledge of these electronic symbols can weigh in
.
I'm thinking it's some kind of voltage spike protection for the BCM
.
But since the BCM is protecting the Power side of this circuit, I'm thinking this is resistance in the Ground side that's heating the brake light sockets
.
Here's an idea, refer to the wiring diagram for the wire colors. Pinch the Power wire to a brake light between your forefinger and thumb. Pinch the Ground wire with your other hand the same way. Have somebody hold the brake pedal down. Which wire gets hot?
to me it looks like they're indicating the lamp socket is grounded to the body of the tail-light assembly, but I'm not certain.
So maybe either @imperator or some other forum guys who have better knowledge of these electronic symbols can weigh in
Here you go. It's in the manual ...
"Incomplete Physical Splice"
I don't think it's significant
Thanks Joe. After I asked for your assistance, I looked at the physical wiring harness (there is no pigtail coming off of it like that) and the tail light assembly (there is no circuitry in there) I was still bamboozled
.
Thanks for taking the time to research that and clearing it up for me
.
YOU are truly da' (mountain) MAN!