1998 malibu question anyone please help

[drgnblze]

hi, i'm working on my girls car after her family has been driving it without any water in it and the car over heated, and they wonder why??..lol.. but anyways here are my concerns and questions:

1: the radiator fans aren't turning on even when the temp gauge is reading red lined, but they turn on when the a/c is on, so i know it couldn't be the fans, what could it be or where do i look at?

2: changed the thermostat with a new one and i'm also doing the anti-freeze flushing since i'm going to use the bar's leaks head gasket repair product to possibly try and fix the issue, my question is did i do something good in changing the oil it already had or should i have left the bad oil in?

3: even when i changed the thermostat with the new one shouldn't of the tempature gone down alot even though i flushed the system

[taillight]

It could be the temp sending unit. There are 2. one for the guage and one for the fan. The one for the fan is controled by the computer.

[la1]

was there water in the oil ? if so the bars leak will not help. The temp sending unit on the motor will not register the correct temp if there is insufficient coolant and / or it has turned to steam