Air Conditioning - A/C seems to take too long to cool the apartment

I recently had the system serviced, it needed a new capacitor and freon. Since then the frost on the cold pipe has gone. But it still takes a very long time to cool the house. I measured the intake air temp last night, it showed 75F. Then I measured the output temp, it showed 51F. Is this a good temp differential? Is there anything else I can check?

That's a great differential. Actually long run times are good. It gets rid of the humidity in the home.

But it still takes a very long time to cool the house.
You do keep it on???? The filter is clean the coil clean. A 24o drop is good if thats for sure. Most of the time a 16o to 20o drop over the coil is good

Thanks for your comments. Good to know the temp. differential is good

Ed Imeduc, I have replaced the air filter a week ago and yeah, it still takes a long time to cool down the apartment. I did not/do not leave it on. I had it on for a few hours and it had made very little difference. But next time I am going to set the temp and leave it on and also keep an eye on temp to see how far it comes down. Anyhow I am wondering if the fan is not strong enough, I mean I am guessing it is not blowing hard enough. I suspect if it moved higher volume of air it would bring the temp. diff. down and probably cool down quicker?

How big is the Apt.? How many BTU is the A/C? how hot is the apt?

The unit may be undersized, and may not be able to pull the temp down.. Or it's too hot, and it may take a long time..

One time I started our A/C on a 90 degree house, and it took 6 hours to get it down to 76.

Our house was 81 yesterday when we got home. Closed up the windows and turned on the A/C. Within an hour it was 76. Then I realized I hadn't changed the filters! I swapped the filters (which were really dirty), and the whole system came alive and really started putting out the cool air. This is an area about 1700 square feet.

So after running the A/C for over 5 hours and not seeing much of a drop in the temp. I decided to look at the heat exchanger. It had a lot of blockage underneath (only visible when you remove the air filter and look up to it). I cleaned it all out and guess what? The room was so cold within 30 minutes my wife started complaining about being too cold! So we are cool now :) Thanks a lot for your help folks.