If the pressure bottle is not low, turn the key on and observe closely.  If
the blinking stops after a couple seconds and then restarts a few seconds
later, the coolant level controller is triggering and the problem is likely
poor contact at the sender or dirty sender pins.

But if it simply blinks without pause, it's probably a leaky ten uF sixteen
volt capacitor inside the gauge.  Replace the cap or the gauge.  Could also
be the ten volt panel regulator out of spec or gauge bolts need tightening.

Yrs,
d