Safe Coolant temp range

Anything below 230, factory gauges are notoriously incorrect btw

Temp gauge sending unit should be easy to fix tho, you need to find which wire and install a factory sending unit, if your trying to use aftermarket with stock gauges its probably not going to work

When i swapped from a v6 to v8 i just swapped the v6 sending unit to the v8, all my factory gauges work like normal despite it being a windsor v8


Edit: went down and looked at it and its red with white tracer


Btw, the V6 is notorious for blowing the fan relay in the main engine fuse box in front of the strut tower driver side, middle row closest to the engine, looks like a maxi fuse except its all silvery metal, its a PTC relay, it'll conk out the coolant module under passenger side fender that feeds the fans

Check that before anything else, mine went out and it wasnt fun tracing it down to the relay

Best Mustang overheating video ever is How To Cool An Overheated Engine With Julia. YouTube video by EyeHandy
Both the above posts are correct
If the fan does not come on at all it probably needs a new CCRM and or a connector
Watch the ECT pid voltage drop as it gets hot and hotter and hotter
Seems like forever waiting for .6v
Then the fans come on and you are home free
Return to customer and explain that unless it boils over and blows the cap off it is ok
NORMAL says the gauge
It will be clear up by the A or L before the fan(s) comes on