Help!..its going to get chilly

ok,1st thing..If this has answered before,I apologize.Heres the situation...95 wndstar,3.8v6.The thing started blowing cold air outta the heater the other morning and the heat gauge went really warm(like still in normal range but close to overheating ) as I was in line for a coffee.I tried reving it up a bit but then the gauge went back down to normal and heat poured out momentarily.I headed to work and the gauge is up and down like a Mariachi band,and heat/cold too!I installed a new thermostat and filled the rad back up today but it still is very erratic in heating and cooling and the gauge is still doing this.Is it my waterpump?.I dont think its the headgasket as no white smoke,no antifreeze in the oil etc.Ant help would be appreciated.Patrick

ok,1st thing..If this has answered before,I apologize.Heres the situation...95 wndstar,3.8v6.The thing started blowing cold air outta the heater the other morning and the heat gauge went really warm(like still in normal range but close to overheating ) as I was in line for a coffee.I tried reving it up a bit but then the gauge went back down to normal and heat poured out momentarily.I headed to work and the gauge is up and down like a Mariachi band,and heat/cold too!I installed a new thermostat and filled the rad back up today but it still is very erratic in heating and cooling and the gauge is still doing this.Is it my waterpump?.I dont think its the headgasket as no white smoke,no antifreeze in the oil etc.Ant help would be appreciated.Patrick
Feel the top and bottom radiator hose both should be hot. I've have gotton bad thermostats and check before installing. A plugged radiator and a badly corroded impeller in the pump can also cause this.

If I feel either top or bottom hose is cold,can I assume the pump is toast,or is a rad flush my next step?Also,which hose (that may be cold) is the tell-tale pump problem hose?..and thank you so much for your quick response,Im in your debt here.

If I feel either top or bottom hose is cold,can I assume the pump is toast,or is a rad flush my next step?Also,which hose (that may be cold) is the tell-tale pump problem hose?..and thank you so much for your quick response,Im in your debt here.
A top hose might be a bad thermostat. If both are cold your not getting circulation. Depending on your cash flow pull the pump and if it turns and looks good replace with a new gasket. I've generally found a plugged radiator or thermostat but have found bad pumps. Make sure the hoses have internal springs as they can collapse.
Make sure the impeller is tight and not slipping.

thank you so much Rhandwor,ill check it out! again thanks for the speedy reply!