Temp Light Coming On...why ?

[john68c10]

Okay,

68C10- 350sbc

Truck has been sitting for about 6 months while I've been working on suspension & steering.

Took it around the block (5 min) today and the temp light came on. About 1 year ago, I put in a new temp sensor.

The radiator was about 1/2 gallon low. Lower and upper radiator hoses were hot, and both heater hoses too.

Fan is spinning, shroud is on.

I'm thinking if the thermostat was stuck then both of the hoses wouldn't be hot would they ?

Water pump ?

Honestly, I'm tired from working on the truck a lot over the last few months and don't want to spend much time on this right now. Where would you start ?