I'm assuming you have an EG....

ground the orange wire from the temp switch, if the fan comes on you need to replace the temp switch. The temp switch is located in front of the thermostat housing with two wires running off it. (black and orange)
If the fan does not turn on replace the fan relay in the under hood fuse box.

the manual states that there is 142ohms at cold engine, and 49-32 ohms with warm engine.
Since the gauge supplies voltage to the sender the only way to know what voltages are right is to get someone to actually pull apart their car for you and measure it. Sorry man it's 21* here (6* with wind) or I'd do it for you.

BTW if you're over 35mph you don't want the fan to run.