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Q: rattling noise

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at start up a rattling to a grinding noise when A/C on but not with A/C off.... noise goes away after a few minutes

My car has 119000 miles.
My car has an automatic transmission.

A: Hi there. The rattling to grinding noise, u...

Hi there. The rattling to grinding noise, upon start-up, with a/c on could be, the air conditioning compressor developing a bearing problem. It could also be, the a/c compressor is fine and the serpentine drive belt tensioner assembly is weak. The additional load placed on the tensioner assembly upon start-up, could cause it to bounce, resulting in noise for a few minutes. I recommend having your vehicle’s rattling to grinding noise upon start-up be diagnosed and repaired by a certified technician from YourMechanic.

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