I have flushed radiator and heater core. No leaking inside car. New thermostat and still no heat. Reservoir is full 50/50 antifreeze/water.
Engine operating fine not overheating. Temp gauge shows normal.
With the engine at operating tempature are the heater hoses warm or hot? If not either the heater is pluged or a shut off valve that is supposed to work when the AC control is set to max is closing the valve at the wrong time. The last possible item is that the tempature selector cable is not attached to the control door.
Try switching to Vent, and turn the Heat way up. If your heater core is working properly is should start heating up, as the engine warms up. Remember your heater should work fine even if your A/C doesn't. If it enven moderately warm up, your going to have get it replaced. That can cost alot more than the stupid part. Try doing it yourself, and save $$$
Remove the inlet and outlet hose connections from the heater core. I'd bet that if you squirted a mild pressure stream of water from a garden hose through the inlet side of the heater core connection, you will see all sorts of "gunk" come out the other side. If this happens, squirt water through the outlet side and repeat back and forth until it appears clean. I had to do this on my SS. Once I "purged" the heater core, the heater got hotter than Dante's Inferno. Give it a shot. Sometimes, a traditional radiator system flush isn't quite enough to open up the gunked up heater core.