Can not get the heater to work

If you have not re-installed the thermostat, then the coolant continually circulates, and will stay as cool as your rad can get it. With thermostat in, it will hold/restrict the coolant to a set temperature approx. 190F-210F and then allow it to flow through for cooling and the cycle begins again. Also make sure you run system with rad cap off for a while with heater on after installing thermostat, to bleed all the air out. Feel the temperature of your heater hoses near the firewall when engine warmed up to normal operating temperature. If both fairly hot, you should get heat, if one hot, one quite a bit cooler, you have a flow problem. That could be a valve not opening, core plugged, weak water pump, for examples. if all that checks out good, then I'd be checking my blend/air door for movement. Let us know what you find.