The engine coolant fan has been running all the time. We replaced the temp sensor thinking that would fix the fan but it did nothing. Also car runs cold, never gets above 130-150 and goes back to almost zero once on hwy. Heater blows only partially warm air.

Check engine light came on, had codes read and said it was the thermostat and temp sensor and that engine was getting too cold. Replaced thermostat (noticed it was loose and was probably staying open all the time), now car overheats with new thermostat as it never seems to open.

Bought another thermostat thinking maybe new one was faulty, still same problem. Flushed heater core as you had suggested to another client, still overheating and fan kicks on and never goes back off. Can't feel pressure in hose coming from radiator, could it be water pump? Seems like fan is sensing heat from part of motor it is near but hot coolant is never making it to thermostat to tell it to open. Please help!