My cold air return blows cool air instead of sucking air

Woops,, did someone install a new blower motor ?maybe running in wrong direction

Happens all the time. LOL

That's one thing it could be.

Where is this return located? 1st floor, 2nd floor, on the floor, on a wall... does this occur with the system running or off? Are there any wedding cakes in the house at this time? Okay, that one has nothing to do with anything...

A blower wheel running backwards should not create enough air force to blow air out the return air duct. The high amp draw from the blower motor running backwards will over heat it and in turn shut down. Check for a down or separated return air duct.

Are you positive that it is a return grill, or maybe it is actually a supply. Please let us know

T-Top, why would it overheat, they are meant to run either direction, however you be sure motor blows so air comes out the ducts?
I believe their would be increased resistance.