[s-cars] heater problem

[Jerry Scott]

I turned on the heater in my 93 S4 today and only cold air came out.   I
tried the Auto setting and the manual setting but no change. All of the
controls seem to work just fine including the blower, but no heat.  The
car water temperature  seems to be in the left third of the gage.  Is
this normal?  I'm thinking it may be the thermostat, but when I feel the
radiator hose under the hood, it is seems hot enough to run the heater.
Any ideas?
Jerry