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Discussion Starter · #1 ·
I've had this issue for a while with my 2000 V70R where when I start the car and turn on the headlights, the interior lights will pulse for a moment before stabilizing. I didn't worry much about it, but after replacing the alternator B+ cable to the starter, I noticed that it had gotten a little worse, and I could see the headlights doing it too while driving. This only lasted about 20-30 seconds, but it was concerning after starting the car to a 3-4 second illumination of the battery light.
I figured first that maybe the cables weren't tight, but they are. I have replaced all of the battery cables with 4 ga cables, including the grounds. Fuse box accessory cables have been replaced, and I even added an additional cable to that terminal. I also replaced the voltage regulator probably a year ago.

I went ahead an did a voltage drop test on the cables. Results are as follows...
With no load at idle, I have a 10mV drop from the battery positive to the fuse box B+. With the headlights, F&R fogs on I get 33.5mV, then 47mV if I turn on the rear defroster in addition to the lights.
From the alternator B+ to the battery +, I have about 40mV on initial startup with no load, then it settles to around 26mV at idle. With the headlights and fogs on, I see 80mV. With the rear defrost on, it goes up to 110mV.

Battery voltage at idle is 14.24, then 14.08 with the lights on.

Now I know this isn't a big drop, and well within the suggested maximum of 500mV. I'm assuming due to the different lengths/gauges of cable, the voltage difference from the alternator cable to the fuse box cables are to be expected?

Anyway, as far as the rest of the charging system, my battery is only a year old, and the pulsing issue has gone on for way longer. Maybe it's time for a new alternator?
 

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1998 V70 T5 5-speed
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I believe that sounds like the alternator going bad.
 

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17,156 Posts
Sounds like alt voltage regulator. Cheaper to replace alternator as a whole unit
 

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Discussion Starter · #5 ·
Yeah, I'm thinking an alternator is the last piece of the puzzle anyway.
 
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