My airconditioning unit inside the house is making horrible screeching noises when the a/c is on. It comes and goes at random times. It will disappear for weeks only to return and last anywhere from a few screams to a whole night then disappear without a trace. There is a big logo on it that says Standard and it only does it when the ac comes on and seems to slowly stop when I turn it off during the screeching.

Thank you for any help.

Sounds like it's coming from the blower or motor. If it's an older model, could be the belt or pulley. With the unit running, pull the access panel off and push in on door switch if it has one to keep running and listen in that area. Many motors have oil ports where you oil the motor, usually one on each end