Our 2005 Sonata GLS with 100,000 miles has a digitally controlled system for the heater & A/C. For more than 2 years the only way to get heat was to raise the temperature up into the 85 - 90 degree range. Now we must put it all the way up to 90. When we do, the heat is extreme.
When was the last time you had the cooling system flushed and bled?