What is the rattle in upper right side dash in '01 Honda Accord? Starts at 1 to 2K RPM. Stops. Again at 1-2K RPM?

Is the coolant/heat system involved, because on cold days, there's 0 to light vibration. Is this Honda known for vibration of its heater core unit? Or water lines to it. Seems up near the dash firewall.

Anyone know of a way to check this without removing the dash, which is close to an all day process.

I've had a rattle in the upper left of mine since almost day 1. Somethings a bit loose in all that plastic. Take the glove box out and feel around

Check the interior heater fan, once had a small rodent burrow in and died when I turned it on.