My 2001 ford Taurus heating temp gauge is not constant on dashboard. It goes up and down. I don?t have heat. Water pump, thermostat, in and out pipe and coolant are changed. Still no heat.

Start the engine when cool, remove rad cap and start engine and let it run with the heater on. (not defrost) Top up coolant as needed in rad, and let it run until either the rad fan comes on and off 2 or 3 times, or you can see increased flow in rad from thermostat opening. It will obviously happen after it reaches operating temperature, so watch after gauge gets close to there. Wait until you see that flow 2 or 3 times or fan comes on and off before you put cap on, and fill return bottle to proper level as well. That should cure it, by getting air out of system, and coolant flowing through heater core.

Heater is not heating?