If you use your heat pump on a regular basis, you should change the filter about once a month. You could probably get away with only changing the filter once every three months if you only run the unit periodically. Keep fans and coils clean and free from debris, and have your heat pump inspected by a professional once every year or two.
Common problems with heat pumps include low airflow, leaky or noisy ducts, temperature problems, using the wrong refrigerant charge, rattles, squeaks and grinding noises. If you can, try to isolate the location of the problem. Is the airflow only low coming out of one register, or do all registers have low airflow? Is the offending noise coming from the air ducts or within the heat pump unit itself?
There are a few things you can do to identify and possibly fix a heat pump problem before calling for professional help. First, if the unit isn’t working, try resetting its motor. Check the pump ignition system for problems, and make sure you don’t have a tripped circuit breaker or blown fuse. Check the thermostat to make sure it’s working properly. Change the filter if it’s dirty, and make sure there are no airflow blockages. If the air ducts are making noise when they expand and contract, you could try putting a dent in the side of the duct to make the surface more rigid. Rattles may be fixed by fastening loose parts, and if you’re hearing squeaks inside the unit, you may need to replace or adjust the fan belt connecting the motor and the fan. A grinding noise may indicate that the bearings on the motor are worn out, which will require the help of a professional to fix.
Keep in mind that if you aren’t mechanically inclined then you probably shouldn’t attempt to do this kind of repair work. And because heat pumps can contain hazardous materials, that’s another good reason to get some professional assistance. A chemical leak is bad news and you can easily injure yourself handling a broken device.