88 560 SL Overheating

[8092400e]

All,
I searched the posts and could not find my symptoms.

The temp climbs rapidly while sitting at an intersection (a bit above 95) when moving (50 mph) it drops to 85 or so (thats all a best guess based on the less than specific temp indicator)

I get only moderately warm air out of the heater, sometimes cool and then sometimes hot.

It seems symptomatic of a sticky thermostat, the radiator is 4 years old, the coolant is MB coolant replaced 2 years ago.

The car has run slightly over 80 since I have owned it (3 years) but never like this.

Also at what temp do the electric fans come on? That has not happened yet.

Thanks-

John