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internal88, Mechanic
Category: Volvo
Satisfied Customers: 2543
Experience:  I've been working on Import and European vehicles for 15 years. Diagnostic is my specialty.
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My battery light went on a few weeks ago, and it pulses now,

Customer Question

My battery light went on a few weeks ago, and it pulses now, as does the engine when it is idling. Everything pulses - dash lights, blower. The car has never died. I checked the battery the other day and it was at 37%. I recharged it, and checked it today and it was at 82%. So I took out that battery and put in a newer one. The battery light stayed on and everything was pulsing. So it's not the battery. It seems that if it were the alternator, the battery would discharge much faster. I've taken a 240 mi trip with the battery light on and it never died, although the pulsing got VERY strong by the end of the trip. Even my headlights were pulsing. Any idea? I have a 1999 Volvo v70 xc (5 cylinder) wagon.
Submitted: 1 year ago.
Category: Volvo
Expert:  internal88 replied 1 year ago.

Hello, I'm Brandon.

It is the voltage regulator in the alternator that is causing the problem.

Once you replaced the alternator you should not have any more issue.

Make sure to check condition of the belt that is driving the alternator.

Please rate me positive for the prompt serivce, THank you.

Customer: replied 1 year ago.
Could it just be the belt? Or is it for certain the alternator.
Expert:  internal88 replied 1 year ago.

Yes, it could be just the belt. It is best to look underneath the belt to see if the belt has cracks condition. Also make sure it has a tight tension.

You could check the alternator by using a voltmeter to see if the output is giving you 14.6v steady.

Customer: replied 1 year ago.
When my daughter's alternator went out, the car slowly shut down, lights went off completely and car died. It happened just like that, just drove to a dead stop, with everything slowing down, dimming.Mine has never done that - it literally pulses, like a heart beat: the engine, the dash lights, the fan. It's an audible pulsing sound because the engine is doing it also.
Customer: replied 1 year ago.
Would the regulators in the alternator affect the car's idle? Seems odd.
Customer: replied 1 year ago.
At an idle, even the rpm stick goes up and down about 5 little marks - very consistent. The whole damn car has this rhythm going through it - can that all be from the voltage regulator in the alternator?
Customer: replied 1 year ago.
As a side note, about when this all started, my mpg plummeted. I am lucky if I get 11 mpg now. Alternator, too?
Expert:  internal88 replied 1 year ago.

Sorry, it was late last night.

Yes, it is the whole alternator unit including the regulator inside that will have affect on your experience.

I'm assuming you installed a good new battery inside.

About the MPG - is the check engine light ON? because this have nothing to do with the alternator.

Expert:  internal88 replied 1 year ago.

I would like to follow up on the issue?

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