yes Jim,,,

it's a mystery for me too... it supposed that the 700Y voltage regulator is
for both gas and coolant temp gauges but the gas gauge is working and the
temp gauge is NOT...

now a question if I may... when I ground the sender wire, the coolant gauge
needle went to the max with a blinking light... - does it mean that the
coolant gauge is working good? or does a bad gauge could doing that too?

thanks