Belt squeal when lights on - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 09-06-2012, 11:27 PM Thread Starter
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Belt squeal when lights on

1971 MB 220D - runs fine during the day but at night when I have the lights on I am getting a squeal from the belt - is a new belt and it is good and tight - or maybe not? Is this just extra load from the alternator causing belt to squeal and it just needs tightening some more? Or something else.

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post #2 of 3 (permalink) Old 09-07-2012, 02:45 AM
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Yes, it's the extra load from the electrics causing the belt to squeel.
If the belt is new and tight I would recheck the adjustment and I would look for the reason causing this, could the battery be a little on the old side or too small? so therefore not able to keep up with the demand.

The battery stores the energy that the alternator produces, if there is not enough energy/current stored in the battery, the system will rely on the alternator for power.

Being that your car is a diesel, once the motor is started you can take out the alternator and battery and she would still run, everything else relies on the battery for power, if there is not enough juice the alternator takes over.

I hope this helps, and guys, if I'm wrong please correct me.
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post #3 of 3 (permalink) Old 09-07-2012, 09:03 PM
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A new belt often stretches after the first days/weeks of use and will need a second adjustment to fully tighten. After this it should be good for most of it's useable life.


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