2001 Buick Century Lighting Electrical Short

[ledzilla]

So, because my Marauder's transmission blew up again, after 2,500 miles of easy driving after having it rebuilt for the second time, I purchased my sister's old 2001 Buick Century so I'd finally have a second car. However, it seems to have a short in the front turn signals/parking lights. I knew about beforehand, and I'm not too worried about it, but it's starting to bug me. Here's the symptoms:

>> Parking lights do not illuminate (checked the bulbs and the filaments are good)
>> Turn signals flash quickly, but not hazards
>> Front turn signals do not illuminate fully
>> When exterior lights are turned on, the turn signal indicators on the instrument cluster light up

I used to know how to resolve electrical shorts, but it's been more than ten years since I last needed to do so and I can't remember what I need to do. Initially, I'm suspecting a problem in the front lighting assemblies, and replacing those would cost a lot less than a single Marauder headlamp, but I don't want to be throwing parts at it like a fool.

And hopefully it won't be too long before I can get back under the hood... This cold snap froze up the hood release. Thought I greased it up enough, but I guess I was wrong.

[Peteyg]

Check the harness and connectors first.

[EMAS]

You do not have a short, a short would cause it to blow fuses. What you have is an open or very poor connection.

The fact that when you turn on the headlights (actually the parking lights) the turn indicators come on, the turn signals don't work up front, the parking lights are dim up front and the fact that the turn signals flash quickly all indicate that the front parking turn socket is not properly grounded.

Turning on the headlights and the parking lights coming on dim and the TS indicators lighting up is because the TS and parking light filiments share the same ground so the current is finding a path to ground through the TS filiment and then back through the TS indicator and finally "finding" its ground.

You can look up diagrams at autozone.com if you sign up for a free account. In there you should be able to find the ground locations and see if they are shared. If that checks out then the tab on the side of the plastic socket can some times loose its spring so it makes poor contact.

Fix the front grounds and the bulk of your problems will be solved.

As far as the hazards I'd start with the fuse and flasher for it, it is a separate fuse and flasher since the hazards are always hot and the TS is only hot with the key on.

[cpe6]

Where did you have the trans built...?

[ledzilla]

Sorry for the delayed reply. Things got nutty and it took a while to get back.


You do not have a short, a short would cause it to blow fuses. What you have is an open or very poor connection.

The fact that when you turn on the headlights (actually the parking lights) the turn indicators come on, the turn signals don't work up front, the parking lights are dim up front and the fact that the turn signals flash quickly all indicate that the front parking turn socket is not properly grounded.

Turning on the headlights and the parking lights coming on dim and the TS indicators lighting up is because the TS and parking light filaments share the same ground so the current is finding a path to ground through the TS filament and then back through the TS indicator and finally "finding" its ground.

You can look up diagrams at autozone.com if you sign up for a free account. In there you should be able to find the ground locations and see if they are shared. If that checks out then the tab on the side of the plastic socket can some times loose its spring so it makes poor contact.

Fix the front grounds and the bulk of your problems will be solved.

As far as the hazards I'd start with the fuse and flasher for it, it is a separate fuse and flasher since the hazards are always hot and the TS is only hot with the key on.

So, I looked up wiring diagrams a few days ago and found that the side marker lamp and the parking lamp share the same hot lead, and the parking lamp and TS share the same ground. Unfortunately the diagrams didn't indicate the coloring of the wires and the harnesses leading up to each assembly have nine wires for all five lamps (parking lamp, TS, low beam, high beam, side marker). I also checked the connectors to the assemblies and they're in good condition and slathered with dielectric grease. Or maybe the ground is corroded and that fact is obscured by the grease (supposing grease possibly added after connector damage).

So, based on what you're saying it sounds like the bad ground is essentially fooling the lighting system into thinking there are failed bulbs. The trick is going to be determining if the bad ground condition is in the light assemblies or outside the assemblies.

FYI, there's no issue with the hazards. I mentioned them since they still operate normally. I can only assume that it has to do with them using a slightly different circuit than the turn signals.


Where did you have the trans built...?
It was rebuilt by a fellow who's had many years of experience building and rebuilding transmissions. Right now the current thinking is that there were electronics issues at the heart of this failure. The error codes before the trans rebuild didn't go away and new ones surfaced. The internal harness wasn't replaced, and I fear that may have contributed to the issue.

[EMAS]

The flasher for the turn signals is designed so that if enough current does not pass through it it will not flash as a round about way of warning you that a light bulb is burnt out. However a ground problem also reduces the current through the circuit preventing them from flashing. The hazard flasher flashes all 4 corners so the amount of current flowing through it is not reduced as much so it keeps flashing.

If you can access the back of the socket you can figure out which wire is the ground. The ground inside the socket is the tab so its wire comes out of the back of the socket closer to the edge than the wires for the parking and TS which come pretty much out of the center of the socket.

[ledzilla]

Well, I ran into something unexpected. The wires in the harness leading up to the assembly connectors not the same color as the wires in the assembly. I'm not yet sure how to open the assembly in such a way so as to examine which wires lead to which connection. I did determine that the wiring diagram I found may be incorrect. The parking lamp and marker lamp do not share a power lead but they appear to share a ground. Or their ground wires just happen to both be black.

[ledzilla]

Ok, so here goes...

I pulled off one of the assemblies and brought it inside. Being as cold as it is outside, it seemed like a better idea than fiddling around out in the cold since I don't have a nice warm garage. Anywho... I was able to poke and prod my way around the inside of the assembly and was able to trace the wiring a bit. And what it looks like to me is that the marker lamp, parking lamp, and turn signal all have different power leads, but they appear to all share the same ground wire. A black wire leads from each the marker socket and the parking/TS socket, and both appear to join up to the same terminal on the assembly connector. Based on this observation, and that there appears to be no problem at all with the marker lamp, I've come to the conclusion that the problem appears to be in the ground connection for the parking/TS socket within each of the front lamp assemblies. If it was with the ground wires leading from the assemblies through the harness, or with the harness connector to the assemblies, then I should have problems with the marker lamps, as well.

Does this conclusion sound about right? I want to test it out with some clips, wiring, and probes, see if this pans out. I think I could test the harness ground wire with a good test light, but mine always seem to break without being used, so I have to buy another one.

[ledzilla]

I guess I forgot to fill in how this ended. So yes, it turns out that in both assemblies the turn signal / parking lamp grounds were bad. I replaced both assemblies and the problem went away... And now I also have nice looking headlights. =D The sweet part was that the replacement assemblies came with cornering lamps (which were not originally on the car) but it was already wired up for them, so they work. I think I still need to adjust the aim, though. I might have it a bit too high.

[mhzbrown]

I have a 2004 Buick Century (1997-2005 Buick Century vehicles are all the same body style), the front turn signals were both lit but were very dim when either turn signal was turned on. Both of the green turn signal indicators on the dashboard would also light up, neither would flash. The hazard flashers worked fine. The problem was easy to fix. I removed the driver's side headlight assembly by pulling off the two plastic tabs, this takes about 30 seconds. Next I saw there was a black ground wire connected to the body of the car. This wire is a lone wire and was not making a good grounding connection to the car. I unscrewed the screw holding the ground wire to the body, I then wire-brushed both the car and the ground wire. Next, I reattached the ground wire to the car and the problem was fixed. The problem in my case was just a bad ground.