<<The coolant light on my 85 1.9 flashes at start up and continues until
engine and coolant warm up. After warm up there is no overheating and
all seems
normal. My old 85 used to flash when engine started overheating. Is this
a bad
sensor or is something else.? Is there a way to test?>>

First test is to open up the expansion tank cap and see how low the
coolant level is.

If it's all the way up, remove the level probe and clean it with CLR and
stick it back in the tank.

9 times outa 10 the probe is coated with fromunda, and isn't reading the
coolant level right.