Preformed single system maintenance on a 2020 heat pump. Tested all electrical components on the air handler unit. All tested within manufacturer specifications. Client did not have filters at this at the time of inspection. I did let the client know that he has the capability for the 20x25x4 filter instead of the 1 in. I did notice in the air handler the coil, drain pan and blower wheels had dust/debris on them. I proceeded outside to test all electrical components they all tested within manufacturer specifications. Unit was heating upon departure