V70 mysterious clicking sound

[H. Hovaness]

There is a mysterious regular clicking sound coming from the dashboard
area of my 2002 V70 FWD. It seems to be more pronounced in cold
weather. A single click occurs every 8 seconds when the car is moving.
What is causing this? Does it have anything to do with the gas cap
door automatic latch mechanism?

 

[Gemini]

Could be the airco-compressor. It occurs when there is too little fluid in
the system.

Gemini