so its 3 degrees out i head to work, truck hasnt been started all day. on about minute 8 of my 15 minute drive check guage light pings at me i look over and the needle is pegged on high, stayed there the rest of the way to work, just got home and all throughout town it jumped around. and then on the way home it stayed in the middle every once in a while dropping below center, whats goin on?

 

Thermostat??
Coolant leak??
Leak in system causing air and temp probe pegging out??
Water pump??
Start at the easy stuff and work through.
Al

 

Sensor

 

Maybe some ice got caught in the thermostat? How old is the coolant and if it's a reasonible age, have you checked the the protction level. Could have formed some ice that got caught somewhere, slowly melted and coolant flow returned to normal. Truck is 10, going on 11 years old. When was the last flush and replace. Look for the simple things first.

3 degrees already, guess I'm getting spoiled here in mountains of Jersey. So far the low this season has been 15. Of course we did have a damaging snow storm in October and Sandy in November.

 

At three degrees, there should be no ice in the coolant, unless the coolant is below standards anyway.

 

I would check the coolant level if you havent already