Coralife Aqua Chill

[Johnny Reefer]

I fired up my chiller about 4 weeks ago and I'm a bit puzzled. The water temp was at about 82F. I set the chiller for 79F with a 2 degree differential. For the first evening the chiller kicked on and off a number of times and pulled the temp down to 79F. (Nice and quiet, BTW). But here's the thing....I haven't heard it kick in since, and yet the tank temp remains 78-79F.
Just wondering if anyone else has had a similar experience with a Coralife chiller....or any chiller, for that matter. I also have a 300W heater running off the chiller.

Any ideas?

Thanx much,