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Slipping Serpentine Belt Causing Dead Battery?

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The battery is fine, so is the alternator. Both have been tested.

If I let my car sit for more than two days the battery dies and I'll have to boost it. It takes a while to build up a charge afterwards too. I have to let the car run for a good 1/2 hour.

I've had issues with the serpentine belt too. It's noisy, but the sound goes temporarily away if you hit it with WD-40. Last year it used to screech on start-up.

So I'm wondering if the belt slipping may be keeping the alternator from charging the battery.

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10 answers to this question

Posted

Volt drop your power wires bet there toast.

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Posted

Check your tensioner, if its not applying enough tension then the belt slips around a lot of the pulleys and makes a screeching noise. When you spray WD-40 on it, it lubricates the slipping and quiets it, but promotes more slipping. Or you could have a bearing going in any of the pulleys that can cause the same effects.

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Posted

The battery is fine, so is the alternator. Both have been tested.

If I let my car sit for more than two days the battery dies and I'll have to boost it. It takes a while to build up a charge afterwards too. I have to let the car run for a good 1/2 hour.

I've had issues with the serpentine belt too. It's noisy, but the sound goes temporarily away if you hit it with WD-40. Last year it used to screech on start-up.

So I'm wondering if the belt slipping may be keeping the alternator from charging the battery.

+1 on the other comments about the tensioner, if the belt is starting to crack etc, replace it. if it's in good shape, belt dressing promotes traction NOT WD40. One thing that is still a question is what is pulling the battery down in two days if it's condition is good? You have something in your car that is causing a current draw. A good battery should last for weeks without any issue starting your car.

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Posted

Yes,but if alernator is not charging because of slipping belt all of the power needed to make the car run is drawing directly from the battery.That could be the VERY good reason why battery is dead.

So...slipping serpentine belt can indeed cause the dead battery.

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Posted

Volt drop your power wires bet there toast.

This.....

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Posted

Volt drop your power wires bet there toast.

I have no idea how to do that, or even what it means. :huh:

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Posted

I have no idea how to do that, or even what it means. :huh:

http://www.aa1car.com/library/voltage_drop_testing.htm

You'll need a digital multimeter, or digital voltmeter. Multimeter offers volts. Good tool to have in the future when testing resistance on the line in Ohms or Volts. Not very expensive. Check autoparts stores or a department store like Sears.

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Posted

The battery is fine, so is the alternator. Both have been tested.

If I let my car sit for more than two days the battery dies and I'll have to boost it. It takes a while to build up a charge afterwards too. I have to let the car run for a good 1/2 hour.

I've had issues with the serpentine belt too. It's noisy, but the sound goes temporarily away if you hit it with WD-40. Last year it used to screech on start-up.

So I'm wondering if the belt slipping may be keeping the alternator from charging the battery.

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Posted

WD40! That just cracks me up. My GF had a stuck caliper on here MB and a guy stopped to help her. He ended up spraying WD40 on it haha! To say the least that mass things worse!

First order of business is to replace that belt due to having WD40 on it...

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Posted

As binglax said...if youve sprayed wd-40 on the serp belt you might want to replace it. If the belt is making noise it is slipping. If you look with a torch to make sure the alternator is spinning it should be evident either way. If its turning then there shouldnt be a charging issue.

Then measure the voltage at the battery and write it down. After, measure the voltage between the negative terminal and the positive battery cable end at the starter and then the negative terminal to the positive cable end at the alternator and write these down too. They should all be very close to one another. If the batt-starter and batt-alt are very close but much lower than the battery its most likely a bad connection between the battery and the starter (whether it is cable ends or the cable itself). Same goes for any other discrepancy.

If all the readings are good, and the serp belt isnt slipping around the alternator then check your grounds. Similar to testing the positive cables but reversed. Measure voltage between the positive terminal and the ends of the main ground cable (one end goes to the frame near the battery tray and the other goes to the block).

I was push starting my car until i realized that there was corrosion at the starter and one of my grounds. Appearances can be deceiving so use a voltmeter.

Good luck.

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