Heil heat pump makes a knocking noise (see video) switched Hunter programmable thermostat from auto (heat or AC as needed) to heat. Knocking stopped but unit runs aprox 10 mins stops running for around 5 seconds and then starts right back up for another 10 or so minutes and continues this cycle.

Dale Koehn

• 88 Answers
• Posted on Jan 24, 2009

SOURCE: New 14 seer split ruud heat pump makes very loud knocking noise

Well you may want to have a tech come out and check the freon level, but mostly when going into defrost, some units make alot of noise, the freon is reversed in the unit by way of the reversing valve, it makes a whooshing sound like freon is draining off, as far as the knocking noise, could be as I said in the beginning, might be low on freon, but it could be that, this particular unit does this, I have had units make some really strange noises in the past but functioned perfectly, hope this helped, please let us know, thanks again,
mr.grzz