Noisy navien combo boiler?

[JasonGraham]

Could use some ideas. We had a navien combo boiler installed a year ago. About a month ago, it started making a screeching noise. Loud!. Some times it goes quiet on its own. Other times it flashes red " overheat " and the unit shuts down. If I start it again after an hour, seems ok. The installer has retired. Had another licensed plumber look at it. He heard the noise. He contacted the company, they sent him a new 3way switch, under warranty. Noise only got worse, louder, more frequent.
The plumber is having trouble contacting the company now. He seems to be lost, as am I. I know there are lots of wizards here. So, any ideas? Thank you.

[WandaCC]

did you ever get the noise issue sorted out? I've got a Navien unit too and started noticing a similar sound after a long cycle. Wondering if you ended up adjusting the fan speed or checking for any loose components. Curious if a tech visit helped or if you tackled it yourself.

[ayranton]

Mine was doing the same and it drove me nuts. I ended up putting neoprene mouse pad pieces under the mounting brackets and that helped a bit. If you're still wondering how to reduce fan noise, I also cleaned the intake filter and made sure the vent pipe was straight with no sharp turns. That seemed to lower the pitch and volume a bit more.