When my VS gets to 3/4 temp my hi fan kicks in which is normal. However my low fan only come on when i have the AC on. Would replacing the temp sensor/sender solve this prob???
does it overheat?
Sounds very strange to me.
From memory the Gregory's manual says to pull the lead off your temperature sensor (the fat one on the right) and start the car. After a few seconds the low fan should start, and a little while after the hi fan. That will tell you something about the sensor circuit.
Is all I can suggest at the moment.
If you are sure that without the A/C on, only the Hi fan works, then changing the sender with do nothing - for the gauge only. I'd also try a few other things before replacing the sensor.