[s-cars] temp gauge error, '99 A6

[Lee Levitt]

A quick question...

My mechanic replaced the coolant overflow tank on my '99 A6 this week. 
Not long after, my daughter reported that the car was overheating -- 
coolant temp gauge almost in the red and a warning on the dash. Oil temp 
was normal. No other signs of an issue.

After sitting overnight, upon starting, the engine coolant gauge showed 
3/4 hot. Shouldn't it read cold on a cold start?

Does this sound like a sending unit or wiring issue rather than 
something more ominous?

Thoughts appreciated. We're taking a road trip tomorrow and I'd prefer 
to take this car rather than the others...but not if there's any 
question about the cooling system.

Much appreciated.

The car will go back to my mechanic on Tuesday for a formal inquisition.

By the way, the car is black, if that makes a difference. :)

Lee