RG-AUDI

I have an 01' Audi tt Quattro 1.8t with a 147,000 that I recently just bought. On the way home with it after purchasing it temp gauge ran just above cold with no interior heat. I contacted the dealer they advised to change thermostat since it was a California car and I live up north. I changed it and have heat now, but its running at 1 line over normal then it will return to normal (so back and forth). I topped it of with half n half distilled water and g12. My question is could it be a sensor or water pump?

Prospeeder

Try the sensor first, they are notoriously bad. From there you want to actually verify engine temp and see if its hot.

RG-AUDI

I tried the sensor and got it flushed but still running warm. My question is do you think I put in the wrong thermostat? It's a" Murrey premium plus" I got it at O'Reilly. Thanks