need help please

[pinto21632]

i have a 95 ford explorer i had a shop scan it and they told me my ect sensor was bad so i changed it but now when driving it the temp will go up but not all the way to hot then it will drop down to normal then a min or so later it will go back up and down but not at idle try to put the old one back in and it did the same thing but never did it in till i changed the sensor i checked the fan good i checked the top hose it was hot i tryed the heat and i get heat and when warm at first start it will idle rough thats what it was doing before i changed the sensor but the temp thing started after

 

[dogfriend]

You may have some air trapped in the cooling system. When its cold, remove the radiator cap, turn the heater control to full hot. Start the engine and let it warm up while idling, adding coolant/water if needed. Once the thermostat opens (you can tell because the top hose will get warm) top up the radiator and put the cap back on.

Changing the ECT sensor shouldn't affect the coolant temp, it just sends the signal to the PCM so that the PCM can adjust mixture appropriately.