I'm the original owner of a 1720 that I purchased in the mid 80's. It's only got around 800 hours on it and I have changed the oil twice and the air and fuel filters and the trans/hydraulic oil once. Have never touched the coolant and there are no leaks. For the last few years, the coolant light stays on most of of the time. As the machine warms up, the light may begin to flash and may even go out. However my levels are normal. Is this a known thing on these older units?