Replaced h20 pump not sure if thermostat is opening

Smart man using a scanner for the actual temp. Assuming you're not losing coolant....2 things I'd look at here, 1st is you may have air in the system, make sure to purge all the air. 2nd is your fan clutch, I've replaced a few fan clutches in my own Trailblazer. Have had them bad right out of the box brand new. Have had bad brand new fan clutches on 2 of my last Trailblazers. You should hear it engaging especially in stop and go traffic.

I"m not sure what the problem is, this sounds like the engine light is coming on because its overheating and you replaced the airpump and alternator and now you thinks it is the thermostat. if this is correct then yes replace the thermostat and also check the fan clutch, when engine is hot the fan should not spin freely. and last are you sure the engine light is on due to it overheating, if it is due to overheating then check fan clutch and replace the thermostant

If there is bubbles occurring even inside the top part of the radiator (where you have the coolant put in), you may have a leak on your head gasket. You may be loosing coolant through the engine.

could be thermostat but also could be clutch fan,or a bad head gasket.

Make sure the fans are working, and also that there is no air trapped in the coolant system. Good luck

Replace the fan clutch on your radiator fan.

P0128 is coolant operating temperature operating too low. This can be contributed to the Thermostat stuck open or faulty electronic radiator fan clutch. This is common, I had the same issue and replaced the thermostat and fan clutch and had the clutch re-programmed (required) at the dealer. As for the P0410, check the air pump fuse, if blown it will set this code on. Also check the air pump hoses for water and cracks. Hopefully this helps!!

I have a 2004 trailblazer and it keeps over heating at stop lights or while driving slow. I have replaced the thermostat and water pump, but this issue still shows up. It is fine while driving down the highway at 55-65 mph. I have also cleaned the radiator and blew through the fins to clean out the dirt and bugs. Not sure if clutch is operating correctly. How can one tell if it is and are these electric? I know there are approx 5 wires running to the front of the clutch, but not sure if this gets a voltage signal to engage the clutch fan. Any ideas?

its sounds your fan clutch

I had the same overheating problem in my jeep ! My problem was finaly found out to be the clutch in my fan its a different kind of clutch system it work as this. When your jeep gets warmer the tighter your fan clutch gets .While cool your fan moves slowly. now to test your clutch just warm up your jeep and rev it up a bit if your fan dose not pick up speed then it is sliping.What will come out of this is that you fan will the seez and run full all the time. if you jeep dose not overheat wile moving then it is not your thermo stat period.