Kills Alternators / Headlights flicker - MustangForums.com


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Old 05-14-2018, 10:55 PM   #1  
Clapper
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Angry Kills Alternators / Headlights flicker

Just got a 2007 V6 and the alternator looked new but was only putting out 12.7 V so I swapped it for a Reman Ultima 135 Amp Alternator from O'Reilly. After install alternator was putting out steady 13.7 V. Battery tested good. Alternator died (today) after three days while driving and barely got home on battery.

Headlights have flickered since I got the car and that seems related. I don't think that the headlight switch is bad because new led driving lights also flicker same and they are wired to an accessory fuse with no switch. The flicker may be a little affected by RPMs but flicker is pretty steady at idle or speed. I have checked and tightened engine to chassis, chassi to battery grounds. I replaced the three wire pigtail on the alternator and put in another warrantied Ultima 135 Amp Alternator from O'Reilly. For all I know they all come with bad diodes, but who knows. Added a 4g ground from alternator to battery just to be safe this time. Detected a very small voltage there before grounding. Checked resistance between all points (alternator, block, battery) and no resistance found. Engine to chassis ground is tight and good. Headlights still flicker.

I am thinking next step is plugs and plug wires, but I am going to wait a week to see if the new alternator gets killed first.

I have read all the threads out there on Mustang flickering headlights and alternator problems and there are a lot of guesses and lectures about Chinese parts etc. and that is not much help. Also the "Well I have no idea but try . . ." sort of responses are no help. I am already in spend mode getting nowhere fast trying to troubleshoot logically.

What I really want to know is (1) whether anyone has actual knowledge of anyone ever actually solving the flickering headlight issue? or (2) solving the car killing the alternators issue?

From what I have read over the past three days, not one person has nailed this at a dealership or otherwise despite the problem being very common with these cars. God, I hate electrical problems.
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Old 05-15-2018, 05:13 AM   #2  
08'MustangDude
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If your killing alternators, then there's a short somewhere. Also, just because it was a
REMAN, doesn't mean it was a good alternator. Have them replace it under warranty
and see if it kills it again.

If the lights still flicker (pulsate) with the a replaced alternator, then you need to check
the voltage regulator. That can kill alternators if it is internally shorted. A bad battery
can also kill alternator; the battery can become a load rather than a source.
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Old 05-15-2018, 08:04 AM   #3  
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Quote:
Originally Posted by 08'MustangDude View Post
If your killing alternators, then there's a short somewhere. Also, just because it was a
REMAN, doesn't mean it was a good alternator. Have them replace it under warranty
and see if it kills it again.

If the lights still flicker (pulsate) with the a replaced alternator, then you need to check
the voltage regulator. That can kill alternators if it is internally shorted. A bad battery
can also kill alternator; the battery can become a load rather than a source.
I am thinking about the battery and will replace it but I would bet it wonít change anything. The voltage regulator is internal to the alternator so if itís bad we will have another failure soon enough.

I do suspect a mechanical failure in the ground system most, but have tested all the grounds and they are tight and have continuity without resistance to the battery. Itís a stumper.
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Old 05-15-2018, 02:05 PM   #4  
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Quote:
Originally Posted by Clapper View Post


I am thinking about the battery and will replace it but I would bet it won’t change anything. The voltage regulator is internal to the alternator so if it’s bad we will have another failure soon enough.

I do suspect a mechanical failure in the ground system most, but have tested all the grounds and they are tight and have continuity without resistance to the battery. It’s a stumper.

The alternator/headlights could be completely unrelated. To start with you do not have the OEM headlights, you have LED headlights. Cheap Aftermarket LED headlights or improperly installed LED headlights are problem prone and can suffer with the flickering you mention if they don't have the proper resistance built into them or an additional resistor installed. Sometimes they are just completely incompatible with the car. Just to be clear are they LED Bulbs in the OEM housing or are they entire LED headlight assemblies that include LED bulbs? (There is a huge difference).

Bad alternator diodes will usually throw a Cam sensor related OBDII code.

If you can, get your hands on a pair of OEM headlights (or bulbs if that's all you need) and install them, If the flickering goes away, the headlights were the problem for the flickering issue. As for the alternator. I try not to mess with rebuilt or manufactured alternators since they often do not replace certain components because they were deemed "in spec". It's a failure waiting to happen.

If cost is an issue, TYC (look on Amazon or Rock auto) makes a brand new one for about half the cost of anything else out there and it's pretty good quality. I installed one in my car about two months and the reviews have been very positive.
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Old 05-15-2018, 02:30 PM   #5  
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Thanks guys for taking time to respond. Yes, I agree that it is entirely possible to get multiple bad alternators. reman or new, cheap or expensive. I also agree that the headlight flicker could be unrelated to the alternator failures. So here is the updated latest chapter in this sad tale.

Last night I put in the second warrantied reman alternator, rechecked the battery cable and grounds for continuity, resistance and tightness - all good. Serp belt is new and tight with good rotation. Battery recharged and started right up and voltages read correct (12.6 / 13.8). Headlights still flickered. Started right up this morning and stopped at the store, came out and TOTALLY DEAD. No dash lights, nothing. Not at home so no tools but checked everywhere I could and did not see or smell any problems in fuse boxes or anywhere easily accessible. But that was not worth much, I know.

Then, as it is being pulled up the tow ramp - shazam! Dash lights come on, but battery is almost dead. I am think loose wire! People keep saying short, but what about an open? Would an open circuit explain this more than a short. Maybe a short would explain how the battery drained so quickly when there should have been no load? I dunno.

So I had it towed to the only shop in town that seems to have their act together and gave them the whole rundown. They listened carefully and seemed to be smarter than me which felt good. I told them my next steps would have been the battery, ground cables, ignition switch, or (eek!) the wiring harness. I know the headlight switch and turn signal switch are also both possibilities, but I think less so and would try them last if I still have any money. The shop said they will try to troubleshoot it and see what they think. I have a business to run so I am hoping they really are smarter than I am and can figure this out before my used Mustang winds up costing more than a new Mustang.

It is now in the hands of the gods. Will this used Mustang ruin me? Maybe. I'll keep you posted of there is some sort of answer to this crappy, expensive mystery. Thanks again!.
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Old 05-15-2018, 04:40 PM   #6  
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So the shop just called and said they found the problem. The positive battery cable was partially melted due to a bad connection and was failing, causing the alternators to wear out and the headlight flicker. I am still not sure how /why, but they swapped it out and the headlight flicker is GONE! Alternator and battery are fine. So I will get the car back and drive it for a while holding my breath. If the problems don't come right back, I will happily return to confirm this victory over the electrical gremlins. If not, I will come back to confirm that they were wrong and we still have a mystery. Thanks!
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Old 05-16-2018, 11:05 AM   #7  
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Crossing my fingers and hoping that you are in luck this time! Post some pictures of your pony!
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