Navien Tankless H/W Heater Clicking Sound Help

[EastVan]

Navien CR-A 240 Tankless Hot Water Heater installed in 2010.
Making an unusual clicking sound as heard in linked video.

Has anyone heard anything like this?

Sound appears to be coming from inlet flow adapter/flow adjustment valve/flow adjustment v/v pipe.
Noise begins at 00:15 (sec) in video part 2.

It appears louder on video than in real life.
Unit drained and filters cleaned.

On another forum someone suggested it was the solenoid for the adjustable valve. Can anyone comment further on how to fix this?

Thanks!

 

[Dana]

If it's the solenoid you should be able to feel the vibe with a finger on it.

From just the audio it sounds a bit like something interfering with a blower impeller or fan, but I could believe the solenoid theory too.

 

[Sponsor]

 

[EastVan]

If it's the solenoid you should be able to feel the vibe with a finger on it.

From just the audio it sounds a bit like something interfering with a blower impeller or fan, but I could believe the solenoid theory too.

Thanks, Dana. I can't get my finger in there but I used a DIY stethoscope and can hear it coming from the solenoid/adjustable valve.