I have an '89 vette with 165 Maf. In Tunerpro my coolant temps vary from about 182 to about 196 on the highway, creep up to about 205 tops when idling around on a 80 or so degree day. Fan is set to kick on at 192 and off at 182 and is working perfectly. Has stock cooling system with 180 stat, but an engine combo that generates alot of heat. My digital dash stock gauge reads about 10 or 12 degrees higher. I think the dash gauge is Is this normal to see a difference? I'm assuming they are fed by 2 different sending units. I don't mind as long as I know which one to trust. By the thermostat temp I think the one feeding the computer is correct.

BTW: After about 100 hours of researching tuning threads I nailed down a tune on my combo that is nearly perfect. WOT kicks ***, part throttle is dead on except for a touch of cam surge below 1800 rpms. I think I have a little self egr-ing going on. This forum rocks for tuning info!

 

The one the ECM trust after all the ECM does control the fans.
Mine is the opposite reads 10 to 15 below the CTS.

 

mine is like garcias' car, the temp gage reads a little lower than the ECM.
replacing the sender for the dash gage may help some.
it may have something to do with the CTS being in the intake and the gage sender in the head.