By is my heater not consistently blowing hot air

What is your question?

I have dual control heat/cooling. Lately my outback has not been blowing warm or hot air. Sometimes it will, but then it will almost instantly loose all warmth. Then it will blow warmer/hot air? What would be the cause for the inconsistency with holding a steady temp on both side of the dual thermostat in my car. Have noticed a bit of a squeaking in my belts, but that dissipates in seconds.

How long has your 2005 Subaru Outback had this problem?

Last couple of days