Does anyone know at what coolant temperature the sensor is supposed to alarm? I have a 1989 John Deere 550G. In the summer, my temperature light will go off after about 30 mins of work. I have added an aftermarket temperature gauge and it will show around 160-180 when the alarm goes off. A handheld infrared gun shows about the same thing when I shoot the radiator hose. I am pretty sure the engine is not too hot when I get this alarm, but there is something inside of me that won't let me keep working the machine with that big red STOP! light blinking.
Your temperature warning switch is probably bad. Older switches were 208*, newer switches are now 215*.
Thanks, exactly what I was needing.