Sounds like the thermostat may be stuck open. How long has it been since it was replaced? If it's been more than a couple years, get another one (with gasket, of course <img src="/forums/images/graemlins/smile.gif" alt="" />) and slap it in and see what happens. That's the easiest way, and it'll keep the fret-factor down <img src="/forums/images/graemlins/lol.gif" alt="" /> Good luck <img src="/forums/images/graemlins/kewl.gif" alt="" />

Doubt it's going to be the sender wire. It wouldn't move at all if it was. Could be the sender, get the FSM out and check your resistance values across the poles before you replace it though. If they're in spec, it should be the thermostat stuck open <img src="/forums/images/graemlins/kewl.gif" alt="" /> Simple fix!