I changed the coolant on my bird today.
Now the temp light is intermittently coming on, though I doubt the engine is overheating. Never happened before even in summer.
What could I have possibly done simply by changing the coolant?
Is it possible I messed up the thermostat just by this simple fluid change? (I just drained coolant, refilled with water and ran for 10 minutes to flush, redrained, and then filled with good old green glycol-based coolant (Prestone).
Easy answer/solution? Give it more time to sort itself out over the winter?
Thanks

check the electric connection..... I had that once too...yrs ago...loose connection, reason I did nt think it was too hot, I have an aftermkt temp gauge also.

also, see if it kicks out water after stopping the engine...
and if you have a stock system ,make sure its not filled over 3" down from the neck when "full" at cool...
the electric 'idiot' light shouldnt come on until about 245F or more I think...so just red flickering light is probably not over heating

Did you mix it 50/50? Check the level cold. I would then drive it and make sure you turn the temp. control on the heater to hot so there aren't any air bubbles in there. Then let it cool and check level again.
Barry

Could be an air lock? Did you run your engine and fill it as the thermostat opened?

Thanks.
1. May be overfull. Would that affect temp light?
2. Where is heat sensor to check wire? Top front of intake manifold?
3. I just filled it up with engine off, then topped it up with engine on. Have no idea if thermostat was open.
4. If air bubble, will running with heat on fix?

Yes I mixed it about 50/50.

Overfull it would just bleed off...sensor should be front right side of the manifold for a V8. Check or wiggle the connector, or pull it off it could be oxidized or corroded.

Running with the heat on will not change anything, as the coolant is always circulating thru the heater core.

The way you describe the before-and-after, its probably the electric sensor switch connector on the manifold. Maybe it got bumped/crushed/disconnected.