98 Sable - Strangeness of Pulsating Lights

Recently my headlights, dash lights, radio readouts and backlighting, dome light, tail lights, etc... have all begun pulsating intermittently and at a
steady rhythm. Revving the engine a little does not stop the pulsating, nor does it affect the tempo of the pulsations. Then all of a sudden it'll stop pulsating and everything will be normal. This happens even when the A/C and radio are off.
Now I don't know for sure if this is what caused it, nor am I 100% certain that this is when the problem started, but a few nights ago I was asked to give someone a boost with some jumper cables. I'm not sure if there's any way that could have affected anything, but it was after that when I first actually noticed the problem, I think.
I checked the battery cables and they're good and tight... so tight I can't even move the sleeve around the post with my hand.
My friend has a '98 Taurus and he claims his lights pulsate, too, but I'm not sure if we're talking about the same thing or not.
Any ideas at all about this one?
Thanks, Damaeus
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On Sun, 07 Nov 2004 08:59:03 +0000, Damaeus wrote:

Hi Damaeus,
It sounds a bit like this pulsating may be caused by the voltage regulator on the alternator. As to the question of it actually being faulty or not..... there are other possible causes that may be making the voltage regulator behave this way.
Have you checked the acid level in the battery? Low level will make the alternator alter the battery voltage by a greater amount when it starts to push charge into it. The regulator may then be sensing the battery voltage being a bit high, and reduce the field current to the alternator... creating a cycle that causes the battery voltage to go between say 12 and about 14.5 volts....
It could also be caused by the battery having some of it's plates not functioning properly. (Either dropped off totally of sulphated up).
I suggest doing a battery test (with a proper battery tester that loads the battery up with a hundred amps or so of load!) Followed by checking out the voltage regulator / alternator for proper functionality.
If the voltage regulator is faulty, you can expect your battery to end up "fried" by being overcharged. Better to spend a little time and or money getting things checked out soon.
Pip
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Ms_Squiggles opined
1. "Ms Squiggles!!!!"? :)
But I agree!
2. Almost certainly the voltage regulator whether or not the battery is near gone.
If you are handy enough to remove the alternator yourself, you might ALSO replace the regulator yourself and save significant bucks - plus the increased likelihood of getting a short life out of a rebuilt.
Once you have the alternator out, it's a 30 minute job MAX.. even if you never did it before. Note the regulator is the module that has the connector with the smaller wires
On your car you may be able to do it without pulling the alt...I dont know
Get the regulator from parts store (suggest NAPA) to match your car/engine type, take the alt part code too. PLUS a replacement brush set.. might as well change them while it's out.      A replacement regulator will vary in price, depending on engine/alt size, from 48 to 75 bucks and that's an OEM mfd (Echlin) regulator.
Compare that to the price of a quality rebuilt alternator.
Alternative: get a whole original alt from a salvage yard
If the battery is original, it's time to replace it. At least have it load tested.
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In posted on Sun, 07 Nov 2004 10:06:45 GMT:

Here's a little more information. I sat in the car with the AC off, radio turned all the way down and just listened while I watched the lights flicker. I heard a single "tap" coming from the back of the car and at the instant I heard the tap, all pulsing of the lighting stopped. I can't imagine what in the trunk could have anything to do with this, but so far I've only had this tap-stop experience once. The next time my lights pulsate like that, I'm going to pull over again to see if I can hear another "tap" at the same time when the pulsating stops. If I can, then something in the trunk might be going bad, but I can't imagine what the heck is back there that would cause this. I mean, the only thing I see back there is some speakers and a trunk lid light bulb.
Damaeus
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Another thing in the trunk of that car is the Stereo system, everything but the controls is located in the trunk.
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Teknical wrote:

And the fuel pump cutoff switch.
--
Mortimer Schnerd, RN

snipped-for-privacy@XXXXcarolina.rr.com
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Problem stems from alternator, specifically a faulty diode(s). As long as the thing keeps charging, no worries! I have the same problem with the alternator in my truck and_have_had it a long time.
Dave S(Texas)
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opined in

Sorry, that's WRONG.
And if it WAS bad diodes, the advice would still be WRONG.. bad diodes often end up ruining the battery by undercharge or draining it.
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Backyard Mechanic wrote:

Depends. A shorted diode would certainly discharge the battery or cause a charging problem. But a OPEN diode would essentially kill a phase on the 3 phase alternator and cause a uneven pulsation. It will still charge, but have less output and the current pulses would be uneven.
I would be more inclined to think its a bad grounding problem if the alternator checks out. I would pay special attention to the main engine block ground, and any firewall grounds.
In any event, the charging system needs a full check out and you need to move on to wires and grounds from there.
Bob
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Bob Urz opined

Well, Bob...we come out fifty-fifty on that. You are right about the OPEN block NOt dischaging bat...and I've seen that open phase pulsation.
Note he said pulse-tempo doesnt change with engine speed?
That points to a regulator problem, some internal component has fried and the reg is folding back, whether due to overcurrent and/or high battery impedance (over voltage)...
So... bottom line, after checking all wiring and grounds - new regulator or alt AND new battery.
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or
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I'll assume turning on and off? Some where there is a short to ground and the circuit breaker is tripping and resetting, thus the "pulsation".
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