Whenever I have the fan on to either the heat or A/C, there is a loud hissing noise which sounds like it's coming from underneath the hood. What could this be? I don't want to take it to a dealer, etc. because honestly I can't afford their costs. If anyone could give me some insight as to what it could be and how I can check it, please let me know! Thank you. (By the law, both the heater and A/C work fine.
