The motor that runs the air conditioner has delicate parts that can easily break. Sometimes, these fan belts & other elements just become worn out over time and with frequent use. Any strange noises heard should be investigated by an air conditioner repair specialist in Des Plaines just to ensure that it is still safe to operate. Always unplug & avoid use until the unit can be inspected. Contact Heatmasters Heating & Cooling or visit their website at https://www.heatmasters.com/heating-and-cooling-in-des-plaines for more information on air conditioner repair in Des Plaines.