My heater is not working properly. I put a new filter in and it started heating really good and then I woke up this morning freezing. I didn't go check the temp. I grabbed more blankets. Later when I did get up the heater was on and the temp was at 64 and a few minutes later it got uyp to 65. Then the heater started making a loud whistling noise.

You need to try and find out where the whistling noise is coming from,, get back to us