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Brake light/turn signal intermittent issue

rob_s

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tl;dr: Has anyone had an issue with one bulb of the brake light and turn signal not illuminate from time to time?

Several weeks ago, I was driving home and hit the right turn signal, and the click noise inside the cabin was fast every other click, indicating a problem. When I got home, I discovered the right-most light on the right turn signal didn't work (so instead of 1-2-3, 1-2-3, I had 1-2-hold, 1-2-hold), and the brake light also didn't illuminate when using the keyless to lock the doors (although the lower intensity taillight did work). The next day, it was happening again, so I stopped by the dealer before I went on a road trip. As I pull from the parking lot to the service bay, it started working again, so I went on my way.

The following week, same thing, and once again, it went away after two drives (start/stop cycles), but I decided to make an appointment for service anyway. They found a TSB and ran a software update per the TSB. Went away for several weeks. Yesterday morning on the way home, it started again, and continued on my way out this morning, but was back to normal on the drive home today (again, after 2 start/stop cycles). I don't know if it has any relevance, but it seems to be coming up on the cooler mornings we've had, when it's been in the high 30s or low 40s.

Any thoughts on what could be causing this?
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Competition Orange

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I have this too. It occurred pretty inconsistently last winter, and by the time I got it into the dealer, it had warmed up and went away.

It just started back up again recently with the cooler weather. I sent a video to my service advisor, and will try to get it in when it's actively occurring.

One thing to note, mine doesn't go away until I turn the car off, I'm thinking some sort of connector issue at the tail light? maybe?

It also seems to activate an abnormal interior signal noise too. I have a video I can upload tonight.
 

HizliBullet

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yes if it goes 1-2 hold it means the 3rd bulb is out, and the frequency usually goes faster than usual
 
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rob_s

rob_s

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ABS550

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Mine too

My right most bulb is doing the exact same thing as you show/describe. Happened for the first time today just after washing the car. Temperature was just a little above freezing.

follow-up
Checked it the next day in the garage and it functions normally.
 
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Competition Orange

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Took the car in, wasn't doing it when I went in, but gave them the video. This is what they said.

Reprogrammed BCMB per SSM 45895.

The service writer said it was a TSB, but that's all that was written on the work order. We will see if this fixes it.
 

ABS550

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Fixed at dealer

When I dropped off my Mustang this morning at the dealer, my turn signal indicator on the dash was operating normally. I mentioned the problem that I had after the carwash. (hand wash BTW)
Then when the car jockey at the dealership jumped in to drive the car into the shop I noticed the right most bulb did not illuminate when he stepped on the brakes. (same bulb that was acting up when signalling)


Apparently, because my vehicle was built after 4/15, it did not need the BCM-B updated as per SSM 45895.
They did however find a loose pin for "circuit CLS53 GY/VT at C499"
All good now. Will report back if anything changes.
 

ABS550

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Happened again

Well, I thought the problem had been fixed. Well it managed to come back today. (10 months after the dealer "fixed it") I pulled the car out of a warmish garage into near-freezing but dry conditions. I had only driven a couple of minutes when I noticed the same uneven pattern on my right turn signal. It was the right-most bulb not illuminating. After driving for a while, the temperature warmed up slightly and the problem ceased. I will undoubtedly be watching this very closely and will report back any further findings.
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