everything ok day b4. 0 degrees outside. on freeway, temperature guage at 1/4. still on freeway after about 12 miles temperature at 1/2 then visibly increased to 260 and light came on. air extremely hot . radiator fan not on. thermostat lock-up???? any suggestions. thank you

For your application the thermostat should be with a safety feature: when is not working is going to block in open position so the engine doesn't overheat.
Your case sounds more like lack of coolant in the system, possible leaking somewhere. When the car is cold the termostat should be closed for a faster worming up of the engine up to the normal function temperature. Because it's easy (not difficult to take off the two bolts from the flange) and cheap I will change first the thermostat and see how it works....you may have the old style that is seized in closed position.:smokin:

I don't agree. A low coolant situation would cause cold air to be blown from the vents. Only a special "fail-safe" thermostat locks in the open position, and over 90% of people don't have one installed. I would have to say, based on the given info. that the thermostat needs to be inspected closer as the possible cause.

i had the same problem and the problem is that your fans are not getting power i had to put in relays to run them all the time but anm still looking 4 a better way