> If coolant has not been changed in the last year.....change it.

The coolant doesn't have to be new within a year to make the blinking light
turn off.... this may be a good idea as regular maintenance (though many of
us change it every two years), but it should not be a factor is solving the
blinking light problem... unless the coolant is perhaps many year old :)

Most likely he either has not a high enough percent of coolant in the mix OR
the coolant is just too low OR the sensor / plug is bad... or the
wiring/ground...

Bill

Bill