Heater was a sluggish today
 

I know the heater matrix in our cars likes to warm it up slowly and quietly. But this morning was a bit chilly.

Remembering that I have a trickle leak at my water pump gasket and that I have not top off lately...

I open the reservoir and it is bone dry. Shouldn't a low coolant light come on?

Yup!

When you turn the key "on" and everything on the dash lights up for "bulb check" are you seeing the low coolant warning light?

Cheers
DD

Upon start up the Christmas lights are on full display, including low coolant.

I'd check the float switch in the reservoir and it's connections.