That's not going to work unless he knows how to pull the electrical cover off the outdoor unit and yank the condenser fan motor wire off of the defrost relay . The outdoor fan will cool any heat brought outside.

If he is brave enough to pull the cover, maybe he's brave enough to touch the defrost test pins and see if it engages defrost AND clears the coil. Maybe he's REALLY brave and borrows some manifold guages and a thermometer and checks his superheat and sub-cooling and compares it to the mfr's chart for performance at his given outdoor temperature.

If he's on a real "roll", maybe he'll pull the cover off the indoor cabinet, put the system in emergency heat, fire up the strips, measure amps and volts, stick his calibrated thermometers in the supply and return ducts, record temp rise and then calculate system CFM and write it on the ductwork for future performance testing, (after he changed the filter and cleaned the coils of course). THEN... he's ready for a 10 minute heatpump compressor run where then he'll again take exact temperature rise measurements, calculate the heatpump's ACTUAL btu output and compare it to the manufacturer's integrated heating capacity chart.

I doubt he'll do any of the aforementioned.

Best thing to do is have it checked by a competent serviceman.