Stealership tells me my coolant temp gauge is bad, need new cluster! Gauge will only come up to the "C" and stay there all day long. When I put a jumper wire between the two terminal the gauge will peak-out. That tells me that the gauge is ok, right or wrong? We are working on my '99 F350, just put a new Ford reman complete engine in. Gauge was working right before, not now. Temp sender has been changed. Stealership says gauge will read high and low, but not in between(?). These are the mechanics that tried to tell me that my sender was down on the front of the motor, not on the thermostat housing! So is it possible that a gauge will work this way?

 

Did hou get the correct temperature sender? There are two different senders and it makes a difference.

 

I wouldn't screw around. They only need a reason not to warrinty your new motor. If there is two senders like stated, buy the other one and see if it works.
Chet