So my car used to have an issue where the cooling wouldn't kick in until far past the center line. I brought it in to someone and they adjusted the point when it should start to really kick in. It started staying at the middle line and was better. I recently replaced my ecm and coolant temp sense and now it's kicking on very late again. What thing was it that changed it back to old cooling?

I had this crappy mechanic work on my car being told he was good and dude cost me 300+ in damages to my exhaust system and now my car misfires after he did my distributor cap.

 

I'm out in AZ. I recently had the same issue and replaced the thermostat with a 180 degree one instead of the 195-215 degree one. I have a 305 TPI and also replaced my cooling fan motor. Problem solved.

 

What cooling do you refer? What is center line? What is middle line?

 

Do you have the 5.0 TBI engine with single fan? Cooling fan turn on temps completely controlled by the fan switch between #6 and #8 plugs on the head which grounds the relay and turns on the fan. How long since it was running cooler? any build up of leaves or junk in front of radiator or condenser? Got plenty of coolant and anti freeze?
It's also much hotter out there than normally. What line on temp gauge are we talking about it being on, and is this highway or road driving?
Do a search on here for fan switch alternate temperature ranges. This is all of course providing that the air dam under the car is still in good shape and guiding air up and through the radiator.
Good luck with it