Quantum Energy AC6 Compact 270L Questions & Answers

Hi Experts, I have a Quantum Energy Technologies Heat Pump Water Heaters. Model name is 200-08AC6-290. It was manufactured in 2015 and installed in 2016. It was making noise. The noise used to be quiet frequent. I used to hear noise for 4-5 seconds every 20 seconds or so. I had called Quantum Energy Technologies. They routed me to a technician. He was saying that compressor is to be changed. He was giving me a quote of AUD 1200 to replace compressor. It was with one year warranty.

I switched off and switched on the unit several times in span of 2-3 days eg switch off for full day and switch on in night. Now fan is not running and there is no noise. What does it mean? Is fan supposed to run continuously. I am getting hot water as usual.

My questions are How the noise has vanished? Is it because the fan is not running any more? Does the fan is supposed to run all time or it does take some rest :)

Reply will be appreciated.