heater noise - sounds like metal crinkling / popcorn maker - is this normal?

[shellprompt]

Hello all - it just got cold here and this is the first time the heater is coming on. I have a noise that I have not heard before. It occurs when the car is cold or the AC has been on and then the heat, so it is obviously caused by heat change. The sound is similar to thin metal being manipulated. This does not sound like plastic changing due to heat. Has anyone seen this before?

and here: https://photos.app.goo.gl/JNBwTu9R6oobB9LTA starting at around 20 second.

 

[wingnutsglory]

Yeah, that's the exact sound I have. It lasts about 5-10 seconds. Must be heating coils, right?

 

[StellarRat]

Normal

 

[MrG_NY]

Heating coils heating up and expanding. This is normal.

 

[mswlogo]

I never heard that on mine. What speed was that at?

 

[StellarRat]

I never heard that on mine. What speed was that at?

I only hear it when I'm outside and the car is preheating in my garage. But, it is exactly the sound the OP describes and the outside air has to be pretty cold to start with.