NO COOL./REFERRAL. Customer stated unit makes a loud clanking noise. She says it started last winter and another company found a loose wire. She said it worked fine all winter long after that but that about a week ago it started doing it again. Customer thinks it could be a loose wire but she says she doesn’t know since it does the loud banging noise and then it runs fine other days. Inspected furnace in the attic and checked all connections. Found nothing loose or disconnected. Checked unit while it was running and didn’t see the cause of the issue. Since this issue is intermittent, the only thing that does this would be a failing motherboard. It was working at this time but a relay might be failing on it. Customer wants to compare replacement vs repair tomorrow after 1pm with a comfort advisor. Unit operational upon departure.