I have a snyder-general furnace and my pilot won't stay on after you turn it from pilot to on I tried evrything... is it the thermocouple or does this furnace have a sensor... and if so how do I change it out... furnace was manufacture in 91...

I don't think that furnace has a standing pilot. I might be wrong. Does the gas valve have pilot or set, on and off on it?

I have a snyder-general furnace and my pilot wont stay on after u turn it from pilot to on i tried evrything ... is it the thermocouple or does this furnace have a sensor....and if so how do i change it out...furnace was manufacture in 91...
It has pilot then u have to turn it to on once the pilot is lit.

Change the thermocouple. It is the cheapest part to change. Then retest.