I have a pentair heat pump pool heater that suddenly stopped heating.  Unit runs, no warning codes, cool air out of the top,  and flow seems good.  However I now hear a buzz like the compressor or switch is bad after the initial cycle but the unit appears to not kick over.  I continually hear a 2-5 second buzz sound like it is trying to work.  Not sure if that typically means the compressor is bad$$$$ or a simple switch?  Any insight is appreciated.  thanks!   
asa strong

Since cool air is coming from the top of the unit, this would suggest that the compressor is still working.  The compressor may be in its death throe, but still working.  Any chance the buzz is coming from the fan motor or fan blades.

Best, Asa Strong
Leona Knox
Have you checked these key points:
1) Check that your heat pump is getting sufficient water flow.
2) Free your evaporator coil from all obstructions.
3) Check the air temperature.
4) Measure the air temperature difference.

After checking all these key points if still the problem persist it would be better to consult an heating service Morris county NJ experts. Most also have experience with heat pumps. A professional is guaranteed to get the system back in operation quickly.
Reasons for the buzz sound in your compressor can be many. As mentioned by Leona , you can check the key points to find the defects. If you cannot find the defect even after the thorough check up then you can consult the professional contractors like heating company Bergen County NJ to get your compressor repaired without the wastage of time and money. Hope this helps you Sean.
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