Originally Posted by BTBC29

First off, check BOTH heater hoses when you have heat and when you don't. An infared thermo is a good tool for this. Start from the heat source and work your way into the air box. SIMPLE things first! There may of may not be a restricting orifice in one of the hoses. The hose will have a solid hard spot in it, this is where the orifice is located. Also, you say you've checked your heater core. The water running through the core needs to be constant. If its restricted, either at the orifice or at the core, the temp will dissipate quickly and since the flow is restricted, it will not return. I would suggest disconnecting both hoses and check for restriction and back flush the core in the opposite direction. Put long hoses on so you can witness that the flow is sufficient and what else may being coming out, like rusty blockage crap. Let me know how you make out. Hope this helps!

Originally Posted by RavenS

Thank you! We found a hard spot in the hose. Now to get that fixed will be great. Thank you again. This is why I check BOTH threads. I had a computer glitch that day. No one else suggested this.