For some reason my heater is making this chirping noise. it doesn't chirp constantly. but when it decides to chirp it might make this noise every 30 seconds or so. it can go on for a few minutes or an hour. unfortunately it's not something i can recall happening under any certain weather circumstances. so i don't really know when to expect it to chirp.
anyone here experienced this? fixed it?

it's not the most important repair i want to make to my car but it'll be one less thing on the list if i could get some help here.

thanx ppl