Heat problem

I have a 92 F-250, my heat works for a minute then blows cold, if i turn it off, then back on, it'll work again for another minute. I read another post for a taurus that said something about flushing the core with a hose. I know a good amount about cars and am able to do maintenance on my own stuff. But I have know idea about heaters systems, how they work and where all the components are. Where is the core, and how do i flush it.

check your coolant level if it is low it wont blow heat does it blow heat when your at idle if it does you need a new thermistat cause it is stuck open

The heater hoses run to the Rt rear corner of the engine compartment..... to the HVAC box. With the engine warm and running at idle, CAREFULLY feel each hose near the HVAC box, they should both be warm with one much warmer than the other. If one is warm and the other basically cool/cold, the core is blocked. If they are as they should be, both warm, then you have a blend door problem.

thanks for the info, i'll check it out and let you know. If the core is blocked, I read somewhere that you can flush it out with a hose. If so where do you hook up the hose and where is the core?

okay, i forgot to check the hoses at idle before i drove off. but after driving, both hoses were hot. if i get up to 40 mph, the heat will work, anything below that, no heat. if i turn it off for a couple of minutes and then back on, i have heat for about 30 seconds, then back to cold, this works both sitting at idle and while driving below 40 mph. When i drove around about 30 mph and stopped i checked the hoses again and one did feel a little cooler, not much though. I'll check it tomorrow before driving. Any suggestions?

Thanks