Hello, I have a 2004 4runner limited. We had a snow and ice storm 2 nights ago, when i went to leave work-i turned on the heater- no problem, a day later in the evening i was driving home and after 5min- the heater (or at least i think its the heater) started making his high pitched sound when the heater was on full blast. i turned it to low and the sound was gone. the next day the heat runs but im barely getting any warm air, and on high it still makes a crazy sound...any thoughts on the problem and how to fix it????

 

That sucks, have you checked your coolant? Next possibly just the fan is the issue, the heat comes from the water from your motor, but the fan blows it. The noise can be from the belt breaking, or similar effect.