Your gauge sender is disconnected or open, back at the thermostat housing.

While you're back there, disconnect the low coolant level sender in
the coolant pressure bottle and verify that this causes the gauge
blinking light to blink after a few seconds.

While you're looking at the pressure bottle, examine it for cracking
at the beltline and in the shoulder between the fill cap and the
coolant level sender.

Yours,
David

At 05:09 PM 9/5/2015, Kk Al wrote:
>We noticed today that the temp needle didn't budge at all. The radiator is
>still getting warm, the heaters still work and the coolant level is fine.
>   The red warning light in the temp gauge  flashes a few times when we turn
>on the ignition, then remains off.
>
>How do we track this problem down?
>
>Thank you in advance