That old low voltage, pulsing light, drop in the idle problem. - Focus Fanatics
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Old 07-25-2013, 06:10 PM   #1
FoMoCus
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That old low voltage, pulsing light, drop in the idle problem.

Well before anyone sends me on a research assignment, I read through quite a few threads on this issue but have been unable to find a cause. My voltage is really jumpy on the dash display voltage test, the odometer backlight, all interior and even exterior lights, and my radio backlight flicker at idle. I know this is going to turn into a novella, but I want to be thorough. I thought the cause was the alternator pigtail, so I wiggled it around a little with the car running, along with other wiring, to no avail.

However, the next time I drove the car after jacking with all the wires under the hood, the car died while I was driving. No lights, no dash display, just a very very dim dome light and the door chime. I assumed the alternator quit charging due to a broken wire and the battery was drained. That wasn't the case though, battery was fully charged. But I did notice some corrosion underneath the battery terminals and the wire was starting to fray a little on the positive cable where it meets the terminal. So I replaced the positive side terminal, went to town cleaning the negative terminal, replaced the felt pads on each side and used di-electric grease on the connections. That brought the car back to the way it was before I messed with anything. I think it may be a little better, but that's probably my imagination. Anywho, I then replaced the alternator pigtail because the lights were still a little pulsey at idle, but that made little to no difference. My alternator is only about 2 years old, battery is only 3 months old, and all my connections look good and tight. Anybody have a suggestion of what else I can try?


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Old 07-25-2013, 06:40 PM   #2
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You found a few bad/corroded connections and already fixed one problem. Good job. Have you also cleaned each of these connections?

Alternator (+) to ->> Starter (+) to ->> Battery (+)
Battery (-) to ->> car frame
Engine (-) to ->> car frame
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Old 07-26-2013, 04:01 PM   #3
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GRAB the battery terminals and see if you can turn them by hand. They suck and often turn (not tight) once you clean them to remove a small amount of metal. The changed one is probably OK, but the negative may twist on you, or loose.

Battery age means nothing if you do not have at least 12.4 volts or higher on battery. 12.3 and lower is dead zone, or problems. Saying a battery is '12 volts' is worthless and proof it's probably not working, or someone doesn't know how to measure one (no insult intended). Give us an exact value there, and while you're at it load test and have it FULLY charged. I've seen plenty of new batteries die in one year. Many issues will crop up to mislead you simply trying to fix car with a half charged battery. You also need to measure the alt output, guessing it has trouble is only dragging out your saga longer. 14+ plus volts needed there. The alt could easily have a bad diode or dead brushes in two years. Many here onsite go at 6 months.

In a PROPERLY working system, dead alt brushes or too low idle from other problems can make flicker. You are nowhere near properly yet though.

X2 to everything Marde says.
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Old 07-30-2013, 02:36 PM   #4
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The connections at the alternator and battery to body ground look clean (but I need to take them off and double check still), the other body grounds look clean, and all connections are tight. The battery terminals are both very tight. The battery voltage reads 12.3 to 12.4 with the car off. When running, I get 14.7 pretty consistently. On the dash, in test mode, the voltage reads between 14.7 and 14.8 most of the time but will sometimes vary into the 14.1-14.6 range. The in dash voltmeter seems to be very sensitive. When the cooling fans kick on the idle drops, everything dims for a second, and the voltage drops down to the 12.2-12.4 volt range, then comes back up.

The battery is fully charged, and the car is a daily driver so the battery is not getting drained. I can turn on all accessories and the voltage holds at around 14.7 until the cooling fans kick then the idle drops and the car stutters. The pulsing lights are present whether every accessory is on or none are on at all. The car idles around 750 rpm or so, the normal idle speed. My guess as of now is a poor voltage regulator, but im not sure how to test that.
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Old 12-02-2013, 06:44 PM   #5
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Hello, I'm having similar problems as FoMoCus - just wonder if anything been found or resolved yet?
 
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Old 12-03-2013, 09:29 AM   #6
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Well I took the fan motor relay out (it's in the fan frame on the backside of the radiator) and cleaned and modified the terminals. They were pretty corroded and melted looking so I cut the wires back and put female connector on, and slid those onto the male terminal connectors on the relay. This helped a bit, but the problem never went away. I bought a new fan motor relay but never installed it, the car got totaled out from an accident last month.

I would start with the relay. I noticed corrosion underneath my battery terminals that I couldn't see without removing them, so I would go ahead and take off and clean them really well also. If it does turn out to be your relay, I'll give you an offer you can't refuse on mine. It's still new in the box in my closet.
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Old 12-03-2013, 10:53 AM   #7
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I'm sure FoMoCus meant to say fan motor resistor instead of fan motor relay. And yes, it is on the back (engine side) of the fan mounting shroud/frame.
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Old 12-03-2013, 11:03 AM   #8
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You DO have a multimeter? If not, then get down to Harbor Freight in your town and buy the cheapie ~ $5.00
Turn the scale to AC Volts them measure across the battery, you should see 0 Volts
IF you do see some voltage then do this same measurement on another car to rule out a flaky multimeter

Do not know how to use a multimeter?
Then go to YouTube and plug in these words:
battery alternator multimeter
There you will find a multitude of videos of varying quality
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Old 12-03-2013, 02:44 PM   #9
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Resistor is what I meant, yes. I also noticed it only really bogged the car down when both fans came on. When the single fan came on to cool the engine it didn't have much effect, but when both fans kicked on when the ac compressor was running or when the high speed kicked in is when I noticed a big drop. So I guess it could also have been a fan motor going bad and drawing high amps..?
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Old 12-03-2013, 03:06 PM   #10
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^^^
I'll buy that resistor, FoMoCus!!

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