What about when you have a unit freezing up and it's not even a year old? Note:It only does this for about a week after I change the filter.Weird.. The guy who put it in had to put some kind of defroster on it because it must have been freezing up then after he installed it. He didn't put a new thermostat in just the unit,don't know that it matters but I thought I'd mention it.I'm thinking he didn't know what he was doing...

If you just changed the filter and it has started freezing go back and look at your filter. You probably have it installed backwards and its restricting air flow

The only systems that have a defroster are heat pumps, and they only defrost during the heating mode. A/C units freeze up due to lack of air flow or low on refrigerant charge or if the system operated at to low a setting on the thermostat, particularly at night when the ambient is down,(should not be run below 70 degrees) or the contactor sticks closed for the compressor, keeping it running, or shorted thermostat wiring. You may have to call a A/C service co. Mike

Should the arrows be pointing up or down on the filter?

The arrows should point in towards the opening.

Yeah,I had them pointing that way.Downward then,towards the opening?