Howdy!

I have a 2010 3500 Cummins and lately I have noticed when I have either the A/C or heat on there is a very high-pitched squeal (and no, its nots the turbo) under acceleration. If I have all the air off, I hear nothing. The google has not been very helpful so hoping to get some ideas to start diagnosing on here.

Thanks for the help!

 

do you notice anything when using the exhaust brake?

 

I haven't used my exhaust brake in a while - haven't been towing much this year so I can't say.

 

Belt squeal? Or from somewhere else? I would be tempted to pop the hood, turn on the A/C, and rev the motor a bit. Bad bearings somewhere will make some rude noises, and it generally starts with the bearing under load.

 

It doesnt sound like a belt squeal but i'm not the most expert at this stuff. If a bad bearing, what do you think it would stem from?

 

Usually the idler pulley bearings go first, or the tensioner pulley bearings.

 

Based on the very basic description, I'd be inclined to suspect either a contaminated/worn/misaligned belt, or a bad belt-driven pulley bearing as well. Does the squeal sound more metallic in nature or more like a car doing a burnout? Do you notice an odor with the squeal, such as burning rubber?

You could try removing the serpentine accessory drive belt and spin each of the pulleys by hand to see if one of them is rumbly, squeaky, or loose. Also, if the belt appears glazed, then consider replacing it. Check the pulley grooves for debris that could also contribute to a belt noise.

-Rod

 

Update. I replaced the idler tensioner and the belt this past weekend, but the problem still persists. I now noticed that as soon as I turn the A/C on an immediate squealing starts so thinking it may possibly the A/C compressor?

 

Did you replace the tensioner assembly??? May be a weak spring there, could also be a failing a/c compressor...... The load the compressors puts on the system may just be the straw that broke the camels back though too.... ANY of the pulleys/bearings that are getting harder to turn may be the culprit....

 

Yes, I replaced the whole assembly. Also did the water pump while I was in there.