Vibrating noise while the heater is running

[Jdananay]

I was thinking similar, would kind of make sense when the defrost is on the ac compressor engages putting a load on the tensioner and idler. What is odd is that it is intermittent and usually happens when the outside temps are in the 30’s. I would think it would be more consistent but I can’t think of anything else it could be since the AC compressor is new

 

[idrivea2022tremor]

The only other thing I've heard make a similar noise is a water pump, but that was on my 1991 Avanti with a Chevy 5.0.

 

[Jdananay]

Another tech suggested idler pulley so I’ll probably start there since it’s cheap