Flickering lights at idle/low RPM - voltage regulator? - MustangForums.com



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Old 09-24-2008, 11:05 AM   #1
TorchedGT
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Default Flickering lights at idle/low RPM - voltage regulator?

So for some reason I thought this would have been a common problem, but I can't seem to see any mention of it on the forums.

I notice my lights flicker pretty drastically when I'm cruising at low-rpms or when I'm at a light idling and such. I THINK the Shaker 1000 bass-hits also cause some dimming, but my electrical background says that's probably just increasingly apparent due to the original problem.

Battery voltage and charge voltage seem great though, cranks right up even after using the shaker 1000 with the engine off for decent periods of time.

So my guess is that the alternator is fine, but the voltage regulator itself is messed up? Has anyone heard of this problem before? If so, is there an easy fix?
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Old 09-24-2008, 11:29 AM   #2
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Any chance you have UDP's?
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Old 09-24-2008, 06:49 PM   #3
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Quote:
Originally Posted by TorchedGT View Post
So for some reason I thought this would have been a common problem, but I can't seem to see any mention of it on the forums.

I notice my lights flicker pretty drastically when I'm cruising at low-rpms or when I'm at a light idling and such. I THINK the Shaker 1000 bass-hits also cause some dimming, but my electrical background says that's probably just increasingly apparent due to the original problem.

Battery voltage and charge voltage seem great though, cranks right up even after using the shaker 1000 with the engine off for decent periods of time.

So my guess is that the alternator is fine, but the voltage regulator itself is messed up? Has anyone heard of this problem before? If so, is there an easy fix?
hey you're not the only one.... i think there is some dirty voltage in our cars. i would love to hook up an oscilliscope and check one of these days!
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Old 09-24-2008, 10:32 PM   #4
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yeah i get the same problem usually right after i start it up and pull away...makes me very uneasy
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Old 09-24-2008, 10:58 PM   #5
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mine was doing it alot, went to the dealership for something else and they did a check of the whole car and said I needed a new alternator, fixed the problem for me....
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Old 09-25-2008, 03:09 AM   #6
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I just had my alternator replaced @ 37,000 miles
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Old 10-04-2008, 07:55 AM   #7
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Sorry I neglected my thread!! Been away for a while, but yikes that's quite a crappy maintenance interval! I'm not even at 30k yet, my M3 had 123k on the clock with the original alternator. sounds like some sort of manufacturing flaw to me. Alternators are pretty simple by nature, they kinda spin and...work haha. If it's working but flickering it's probably the regulator, but I think they are usually integrated into the alternator so the end result is the same. Wonder if that counts under powertrain warranty?

I'm planning on getting HID fogs/low-his as well, which should probably fix the problem (perceptually at least, since light comes from an arc which isn't as prone to voltage fluctuations) it can't be good for the ballasts though.

In any event, you could buy at least one HID kit for the cost of an alternator, so I'd rather go that route I guess.. wasn't sure if there was a TSB issued for it or something

Thanks!
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Old 10-04-2008, 11:32 AM   #8
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It's close to XMas time folks.
It will do that for a while...





Seriously, it's got to be alternator related.
Something is drawing to much juice...
The UDP would cause that as well
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Old 10-04-2008, 01:59 PM   #9
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Quote:
Originally Posted by TorchedGT View Post
I notice my lights flicker pretty drastically when I'm cruising at low-rpms or when I'm at a light idling and such. I THINK the Shaker 1000 bass-hits also cause some dimming, but my electrical background says that's probably just increasingly apparent due to the original problem.

Battery voltage and charge voltage seem great though, cranks right up even after using the shaker 1000 with the engine off for decent periods of time.

So my guess is that the alternator is fine, but the voltage regulator itself is messed up? Has anyone heard of this problem before? If so, is there an easy fix?
What does the ol DVM say while driving around? That will tell you
combined with your electrical background.
Extrapolate on the 'seems great' part of the diagnosis?

Quote:
Originally Posted by eric6913 View Post
hey you're not the only one.... i think there is some dirty voltage in our cars. i would love to hook up an oscilliscope and check one of these days!
Maybe if its not raining I will get the Power Conditioner out and
hook up the Oscope and see what kind of ripple we have.

Last edited by 157dB; 10-04-2008 at 02:17 PM.
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Old 12-04-2013, 05:19 PM   #10
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Okay gentlemen, here is what I found on my 1999 Mustang GT. I get an occaisional battery light on the instrument panel. It is not consistent, had a new battery installed, and had the alternator checked out..its ok. So, here is what I have found so far. To check the alternator, start the car, let it idle and pull off the negative battery cable....must be the negative one. If your car still runs, the alternator is good. If your battery is new and it checks out good, then that leaves only one item left, the voltage regulator. Now, I hooked up my digital voltmeter and found after I started the car it read 14.40 Volts which is normal. After about 15 minutes of running the voltage decreased slowly down to 12 volts and some change. The voltage regulator is suppose to keep a steady voltage to the battery to keep it topped of (charged) and that is around 13.8 VDC. So, for my car, I believe the voltage regulator is not doing its job. I will post an update to this once I replace the voltage regulator to see if that fixed this issue.
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2005, 2007, flickering, fluctuations, gt, hid, idle, idles, low, mustang, regulator, regulators, rpm, rpms, s197, vechile, voltage

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