Honda Civic

'94 Honda Civic EX, 225,000 miles. Car recently started blowing warm air, even on cool mornings, with the vent from outside air, and the temp control all the way to the cool side. I'm thinking the " hot air" is not being shut off completely. What could be causing this, and how can I check it / fix it? I'm reasonably comfortable mechanically, and want to fix it myself if possible.
With summer almost on us, I don't want any hot/warm air coming into the car. We live in SC and already have had temps into the 90's.
Thanks for your help,
April 28, 2006.

Find or trace the cable from the temp control and inside the engine well is the valve to control the flow on the coolant line that feeds the heater for the car. The valve is not closing all the way. A system flush could rectify the problem but you may want to take off that valve and clean or replace it.

Bruce Hunt
Apr 28, 2006.
I replaced the heater control valve last Friday, and it is now blowing nice and cold, with the temp on cold, and warm when temp control is moved to hot.
Thanks for your help!

May 11, 2006.