Toyota Repair: heater problems., celica gt, heater valve

Question
I own a 1987 Celica Gt-s and for some reason the heater will not blow hot except for every once in a great while. its only blown hot twice, both for a very short time. i checked the valve that lets the hot fluid into the heater core and found that the cable didnt open or close the valve when I moved the heat control on the dash. so my first guess was that it had just been closed this whole time because the second time the heater blew hot i checked and found that the valve had opened as if the cable on the valve arm was pulling like it should be. after it started blowing cold again I pulled the cable off the valves arm and manually opened it, but it still wont blow hot. after opening it i felt the hoses and they had hot fluid running through them. is it just a bad heater core or what?

Answer
Yes, it does sound like the heater core is blocked or partially restricted but before assuming this remove the heater valve and check to see if it actually opens on the inside, I have seen heater valves move the lever but the shaft inside was broken and didn't open the valve. Both hoses will still feel hot even if there is no circulation through the core.