heater not getting hot

Hello. This is my first post and your help is much appreciated.

Heater output seems to only get hot if the engine is rev'd for 5 minutes or being driven to maintain the rpm's high.
1) Thermostat OK? The temperature gauge reads around the 1/4 mark and fluctuates higher a division or two higher then returns to the 1/4 mark. As I recall it always seemed to read that way. It never was up near the 210 degree mark.
2) Temperature control OK? The temperature control seems to operate in that I can go from the cold to hot position and get cold to warm (and sometime hot) air flow in the truck.
3) Hearter core OK? not sure. Even though I can get some heat, could a clogged core result with the tempermental warm to hot scenario I explained above? The hoses going into the core both seem warm/hot. The output hose is not cold unless just the engine heat convection is fooling me. I tried to pull the hoses off the core to try a back flush, but I didn't have any luck removing the hoses. I was afraid of stresssing the hose connections at the core. Should this be of concern?

Any ideas?

what I would do is back flush the heater core I am assuming that you had dexcool and gelled up in your heater core. take both hoses off your heater core take a garden hose and turn on the water should take care of the problom

Yes. it is a 1997 with Dexcool. Is that prone to clogging up the core? How flimsey are the hose connections to the core? I couldn't get the hoses off and I'm afraid of bending or braking the connectors.
Thanks for the feedback.

try to disconect hoses from the other end not from core

yeah I should of been more specific. its easeir and also dont want to break the heatercore

Thanks guys! I'll try it tommorrow morning.

You should really use something like Prestone rad flush too.
If you have a compressor blowing the system out afterwords will really get rid of a lot more junk.

When you re-connect everything try filling the system through the top heater outlet, and it will fill the heater core... otherwise you'll have an air pocket in there, and no heat.

when the water level is low in the radiator it will cause no or little flow to the heater core.sounds like your problem.

any progress?

check the thermostat it might be stuck open