i have a 1995 Explorer,5 speed, and heat gauge goes up and down, why? on 1995 Ford Explorer

it only triggers the overheating light when going up a hill, and when i slow down the gauge will go down as well. What is the problem?

Asked by for the 1995 Ford Explorer
you probably have a flow issue. thermostat stuck or radiator has blockage or restriction in it. the debry settles to the bottom of radiator and builds up and tubes plug
so... replace thermostat and flush out radiator maybe? Thank you very much!!