Oldsmobile/Buick: Luke Warm Heat In Car, oldsmobile ninety eight, heater core replacement

Question
I have a 1987 Oldsmobile Ninety-Eight Regency. The problem I am having is with the heat in the car only getting semi-warm.  I have the Automatice control, that allows you to select the Temperature 60-90 degrees (lighted display).  After my car has reached operating temperature, I turn the blower all the way up and the heat to the max "90" and it never gets HOT, maybe 65-70.  It Will defrost the window, and car is not cold but definately not 90 degrees.  If I rev the car up and HOLD, gets warmer, but wont stay hot.  I just changed the thermostat, and had a mechanic blow out the HEATER CORE hoses with a air hose (per his advice).  I understand there are 2 things left. HEATER CORE REPLACEMENT and The heater control valve (or Lever)?  I did try the "TOUCH the hoses: when the car gets to temp near the heater core, and they seem about the same temp.... ANY ADVICE  PLEASE HELP>>>

IN MICHIGAN.... TOO COLD

Answer
Che' Eddie ,

Try replacing the thermostat first , if this doesn't solve the problem then it could be a faulty temperature sensor . Plugged heater core could also be the problem .

I'd make sure your thermostat is in working order and you have the correct degree thermostat installed .

Eddie if you have any more questions please feel free to ask . Don't forget to rate my reseponse to you .

Cheers,

Ed McKenna