I have a 39LA carrier chw ahu, 1992 yr manufactured., belt driven. Making whoomping sound from supply duct side of unit, its a deep bass sound, traveling either from unit
I already replaced the entire fan assembley, pulleys, sheeves, blower motor. Belt access door is sucking unusually hard, meaning its super hard to open door. While return side., where the filters are is not too bad as compared to the supply.
Somethings wrong, were thinking the coil is still dirty and needs to be washed again, and fan is causing entire cabinet to pulse creating whoompimg sound.
Please advise with any suggestions.