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post #1 of 9 Old 12-15-2011, 04:57 AM Thread Starter
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Light Pulsate

I have a 2003 Excursion with 7.3L motor. Last week, all the lights(interior and exterior) started to pulsate real fast. I had both batteries and alternator checked by two different shops, they all checked out fine. Any suggestions as to what could be causing this problem?
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post #2 of 9 Old 12-15-2011, 05:14 AM
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I have the same dang thing. I know it's the alternator. I've been meaning to check it myself, along with it's amperage output. Mine is a Duralast with a lifetime warranty. I talked to them, they tested it and this person actually kinda new what she was doing, except for the batteries being in parallel . But she said if it kept having problems, bring it back.



2000 F-350 Lariat Super Duty, Dually, CCLB, 7.3L
4R100, 2wd
330,000 + miles
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post #3 of 9 Old 12-15-2011, 05:16 AM Thread Starter
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Thanks, I find it interesting that I had two independent shops check the alternator and both said it was operating fine. Are your lights flickering fast(2x per second)?
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post #4 of 9 Old 12-15-2011, 05:19 AM
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Hadn't really counted, but you can definitely tell they are pulsing around once a second or so. Actually, it might be even faster so yea. The girl did say it was putting out 14.x volts, which we both found kinda weird.



2000 F-350 Lariat Super Duty, Dually, CCLB, 7.3L
4R100, 2wd
330,000 + miles
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post #5 of 9 Old 12-15-2011, 03:54 PM
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Ok, SOOO.
Readings right off the alt were:
Voltage - Varied from 14.5xV to 14.97V. Seems high to me, not sure what that would mess up, if anything.
Amperage - Went from almost 0A all the way to 40A really fast. So fast, I almost couldn't read what numbers it was showing.
Other than the alternator, obviously, being the main suspect, I have had something sqeaking forever. I think it's either the AC pulley bearing, OR my tensioner is too loose allowing the belt to slip on a pulley and squeak. If it is slipping on the alternator too, then that would cause problems I assume.



2000 F-350 Lariat Super Duty, Dually, CCLB, 7.3L
4R100, 2wd
330,000 + miles
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post #6 of 9 Old 12-16-2011, 08:57 AM Thread Starter
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Thanks for the replies. I ordered a Heavy Duty alternator. Will see if that fixes the problem. I was also told by someone who works in Ford Service there is a module behind the fuse box that could cause this symptom as well.
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post #7 of 9 Old 02-11-2012, 07:38 AM
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I'm having the exact problem with the same results when I have the alt. checked at the parts store. Did the new heavy duty alt. fix your problem
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post #8 of 9 Old 02-11-2012, 07:48 AM
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I finally had to replace my tensioner.
Didn't fix the pulsing. It's the alternator. Probably specifically the voltage regulator.



2000 F-350 Lariat Super Duty, Dually, CCLB, 7.3L
4R100, 2wd
330,000 + miles
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post #9 of 9 Old 02-11-2012, 08:32 AM Thread Starter
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Thanks, I replaced the alternator and it fixed the problem.
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