Temp gauge reads wrong!

[jeffs98]

I have a 78 chevy and it has a new (tried numerous ones) temp sender in it and the gauge reads too high, actually the gauge starts reading that motor is getting warm way too fast!What i mean is that i can start the truck up and in no time the gauge starts rising past the 100 deg mark and on up!
I was told by a gauge repairman that this is not a sign of a bad gauge, he said it is the sender! I was wondering what this board thought as i always get correct answers here and am tired of messing with it! I am to the point now of trying to ohm test wires to gauge to see if one is partially shorted to ground! If the wrong temp. gauge was in it, would it do this or is that possible? Thanks!!
The temperature gauge in it has the temp numbers starting at 100 deg. i have noticed lots of older trucks having the ones that go cold to hot!! Just thought this might help!!