Not sure what causes this tensioner to rattle when the AC compressor turns on. It doesn't rattle when the AC is off. I replaced the idler pulley and this video is from the original pulley, but changing the pulley didn't stop the tensioner from shaking and rattling. Could the tensioner be weak? Should I replace the whole tensioner assembly? Belt only has about 15k miles on it.

See video -

 

The recommended procedure today is to replace the tensioner assy when you replace the belt.

 

I hope that's all it is. Didn't know if the AC compressor might be starting to go since the tensioner only rattles when the compressor kicks in.

 

belt tensioner is a "wear" item and as mentioned should be replaced with the belt.

 

Thank you both! I picked up a new tensioner assembly and will install it soon.

 

Thanks for the update.

 

Check your ac fan and clutch to see if the fan pushes in and out or wobbles front to back.

 

Bob, thank you. I'll take a look at the ac fan and clutch when I get a chance.