Low-beam Headlights Blink [tic]

Thanks for the article Steve, it sums up the symptoms of the problem and I understand what you are getting at regarding the wiring loom etc.

However it's something that is affecting the whole system. I have interior lighting as it's a bus and this flickers in tune with the headlights and indeed does so with them off.

I also have aftermarket fog lights fitted with a basic wiring kit taking the feed to the relay directly from the positive terminal of the battery. With nothing else on, these also flicker at speed proving that the system as a whole is being affected by a current draw somewhere along the line.

What I, and others on here need to find out is what's causing that draw!!!

stroud_omnibus said:

...

What I, and others on here need to find out is what's causing that draw!!!

Click to expand...

Perhaps a DC clamp ammeter with leads out to a remote meter? Then you can move the clamp on current transformer around and observe the readings under real operating conditions. An analog display would be my choice vs any digital reading. The needle will bounce visibly in time with the headlamp blink[tic].

I would start my monitoring out at the battery fuse bank and follow in from there.

vic

MercedesGenIn said:

Here is an interesting read regarding light output vs voltage - it is really quite an eye opener:

''Headlamp bulb light output is severely compromised with decreased voltage. The drop in light output is not linear, it is exponential with the power. For example, let's consider a 9006 low beam bulb rated 1000 lumens at 12.8 Volts and plug in different voltages:

...
All the best
Steve

Click to expand...

You now understand what some electricians never figure out.

"Let's see. My 120 volt 1000 watt water heater resistance element burned out. I have a 240 volt 1000 watt heater that will fit. I'll only get 500 watts of heat, but should be fine." Wrong.

They install the 240 volt heater and don't get enough heat. That is because they only get 250 watts of heat at 120 volts.

Why?

The 240 volt fixed resistance heater supplied with 120 volts reduced 2 parameters, both the voltage and the current. They actually reduce the heater output down to 25%.

Don't believe it? Do some calculations using Ohms Law. It will all work out.

That is what is happening with your headlamp example. The headlamp bulb is a fixed resistance. When the voltage into that fixed resistance is reduced, there is also a corresponding reduction in current. You have just reduced two parameters at once.

Anyway, you provide some good information in your post.

Thanks.

vic

P.S. - It's not an exponential curve.

Hi Vic,

You are correct with the heater analogy.

That text is not mine. its an extract from the article. His statement is correct that the visible light output would an exponential curve relative to circuit power, it certainly isn't linear. For the same reason, as the voltage dropped, the power would reduce as circuit current would also fall with a fixed resistance load.

As you say a lamp is not half as bright at 6v as it is at 12v and I don't think he was saying that in his description. Interestingly a third force is in play - the cold resistance of a tungsten filament lamp is around 1/15th of the resistance cold than it is hot, so there we have another variant in the mix. The brighter the lamp (hotter) the more resistance presented. Basically the light output is a non linear curve with a steeper rise in visible output approaching the lamps rated output.

Ahhhh.. Science...

All the best
Steve

Steve,
Good info.

My wife claims that I just can't let things go.

I would never admit it to her, but she's right.

MercedesGenIn said:

Hi Vic,
... Basically the light output is a non linear curve with a steeper rise in visible output approaching the lamps rated output.

All the best
Steve

Click to expand...

Exponential

Relating to a mathematical expression containing one or more exponents. ◇ Something is said to increase or decrease exponentially if its rate of change must be expressed using exponents. A graph of such a rate would appear not as a straight line, but as a curve that continually becomes steeper or shallower.

Exponential is non-linear. Not all non-linear is exponential. If there is a knee in the curve, is it still exponential?

That said, it is always good when you are involved in a discussion.

It will be interesting to see if the blink[tic] ever gets resolved, or that it just becomes the descriptive term for that annoying Sprinter headlamp phenomenon.

vic

Heres a thought, if we assume we can see a blink tic of some sort as voltage drop, is it worth doing a ripple test on the alternators in the running vehicles with this issue. It is normally accepted to see about half a volt AC across the alternator (or battery as its still connected to the same point) if its more than this then their could be a diode on its way out. Simple test worth a stab with a test meter on AC volts range. Do this test both at idle with lighting load applied, if its easy to set up - leave the meter connected from an accessory pick up point in the cab and see if any readings of substance are obtained in a live blink tic situation. If nothing to report then at least the diode pack of the alternator can be pretty much eliminated.

http://assets.fluke.com/appnotes/automotive/beatbook.pdf

All the best
Steve

Just plain o'l non-linear curve - howzat!
S

MercedesGenIn said:

Heres a thought, if we assume we can see a blink tic of some sort as voltage drop, is it worth doing a ripple test on the alternators in the running vehicles with this issue. It is normally accepted to see about half a volt AC across the alternator (or battery as its still connected to the same point) if its more than this then their could be a diode on its way out. Simple test worth a stab with a test meter on AC volts range. Do this test both at idle with lighting load applied, if its easy to set up - leave the meter connected from an accessory pick up point in the cab and see if any readings of substance are obtained in a live blink tic situation. If nothing to report then at least the diode pack of the alternator can be pretty much eliminated.

http://assets.fluke.com/appnotes/automotive/beatbook.pdf

All the best
Steve

Click to expand...

THAT is an excellent observation.

You would likely not be familiar from the other side of the Pond. Our GM alternators were notorious for having a single diode fail in the "diode trio" voltage regulator. The output would be reduced. Most mechanics would replace the entire alternator. Those who were able to troubleshoot down to the diode trio being the problem could fairly easily and inexpensively just replace the diode trio to restore proper output. (Maybe more of a fix for DIY types and not the pros?)

Anyway, back to topic.

You are absolutely correct that a compromised alternator might contribute to the blink[tic] symptom.

vic

http://www.hotrodders.com/forum/how-check-rebuild-g-m-internal-regulated-alternator-117479.html

FIXED!!!!

It was the rear ABS sensors causing my issue. I tore apart the brakes to gain access to the tone rings (no easy feat on a dually) I had surface rust on the rings. I used a small utility knife to carefully break away any rust chunks, and then followed by a quick sand using 80 grit sand paper.

I put everything back together and took it for a spin, still had issues, but now had new low speed issues. Pulled everything apart again. Pulled out my feeler gauge and measure the sensor to ring distance. Left was .050, right was about .020 thou, BINGO!! I tapped both sensors down until I had .010, put everything together and took it for a spin. No more blink. No more low speed weirdness. No more vibration in the throttle pedal!

I guess I was to quick to congratulate myself. I still have the blink issue, except now, it happens about once every 2/10 of a mile or so... I mean it's progress, I'd say it is at least 90% better than before, (it was every few seconds before) but not cured.

Now I'm really stumped, I've got clean tone rings and adjusted sensors How critical is this the precision on this? Apparently, very.

Now keep in mind I've only owned this van for about five weeks, so who knows what its been put through, and who's worked on it. I noticed when I was in there that someone had just replaced the right side sensor, as in very recently, it was still nice and shinny and moved freely in the bore, and I could still see silver anti seize around the bore. As for the left side, the original, it put up a heck of a fight. It took much banging, prying, and a little heat to get it to move. I'm wondering if I might have injured it in my aggression.

For everyones information, a 5/8 open end wrench slides nicely over the sensor to work as a makeshift puller. I used a small pry bar between the wrench and the axle housing to pry the sensors out. I used a scrap of lumber and a small hammer to gently tap them back in.

I think the only real cure would be two new tone rings and new left sensor. I'm not willing to take my axles apart out in the yard laying in the snow, so I'll have to save this project till summer.

BlackHawk said:

...

Now I'm really stumped, I've got clean tone rings and adjusted sensors How critical is this the precision on this? Apparently, very.
...

Click to expand...

It would be interesting to connect a dual trace oscilloscope to the 2 sensors in question to see if the wave shapes are the same/similar or have some noticeable or major difference.

I presume that one at a time the front compared to back sensor would be a possibility too.

I have no idea whether the DAS, DRBIII has any capability of displaying the wave forms, but they may. To my knowledge the DAD does not.

To my knowledge all the wheel sensors are the same except for cable length. My 2004 left rear sensor was badly seized. When I changed the rear bearing/seal I cut the cable and spliced it back together. It has been fine since the splicing.

Thanks for the updates. As you say at least there seems to be progress. Keep plugging away.

vic

Aqua Puttana said:

It would be interesting to connect a dual trace oscilloscope to the 2 sensors in question to see if the wave shapes are the same/similar or have some noticeable or major difference.

vic

Click to expand...

I have access to a oscilloscope, I think I know what I'll be up to next weekend.

Dragging up this old thread again!

Well, I think (read: sincerely hope!!) that my flickering headlights problem has now gone after spending a fortune over the last two and a half years.

Just over a week ago I went to start her up to do a trip. Been stood for three days. Whirr.... whirr.... click... click. Nothing! Jumped her off my car and off I went. Started fine for the rest of the day and also the next morning but I wasn't happy. Took her to the motor factors who diagnosed a bad battery. They put on a 900 amp Exide, the biggest that would fit in the tray.

No more flickering!!!

Stroud: Has the new battery permanately fixed the issue? I assume prior to replacing the battery, way back when you first noticed this issue, you cleaned off the grounds really good.. can anyone provide the ground location for the abs solenoid off the top of their head???

I’m working through this issue on a 2005 3500. It has the head light blinking and clicking noise coming from under the seat on acceleration especially at highway speed. It has a new Bosch 900 cc amp starter battery and new alternator.

Check abs fuse isn't loose? Mine seems to wiggle excessively. Graph voltage at abs fuse with high quality meter, borrow a snap on or fluke if you must?

SneakyAnarchistVanCamper said:

Check abs fuse isn't loose? Mine seems to wiggle excessively.

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Yes, my ABS fuse wiggled quite a bit.. after a 10 mile jaunt and getting up to highway speed and a piece of tape over the fuse, the issue seems to be resolved. I don't want to completely count my chickens yet, as this was sort of intermittent, but that test drive should have caused the click (tic) sound I would normally hear.

Nice shootin' Sneaky!

vanski said:

Yes, my ABS fuse wiggled quite a bit.. after a 10 mile jaunt and getting up to highway speed and a piece of tape over the fuse, the issue seems to be resolved. I don't want to completely count my chickens yet, as this was sort of intermittent, but that test drive should have caused the click (tic) sound I would normally hear.

Nice shootin' Sneaky!

Click to expand...

never mind.. this wasn't the source of the problem. didn't think it would be that easy considering how difficult it was for others to fix, or not fix, this issue.

I had this random ticking noise under steering area where all the fuse and at same time I was able the hear some kind of solonid noise under the van for last 2 days. This was going on every 10 minutes or so.. after reading this form it made more sense somthing to do with ABS break system that may have triggered as 2 days ago I was working on 5th cylinder fuel injector and I had to remove brake fluid tank and fluid sensor to create more space. I think that was the root course and may have lost pressure on accumulator and kept working on building pressure ? Not sure however clicking went off after I disconnected the battery wire and reconnected. Later today will take it for a ride and see if actually gone,!!

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