Just drove it around town a little bit more today. Light came on in less than 5mi of easy driving. It is butt cold out here today.

Let the truck cool down for an hour or so, then started it and let it idle for about 30min. A/T temp light came on in about that time.

I'm going to say Frank is correct - faulty switch.

My delusion of sluggish performance was either just that - a delusion, or icy roads. <img src="/forums/images/graemlins/scared.gif" alt="" /> I cruised around town today with the light on and the A/T feels like it's performing solidly.

I'll get this thing replaced when I can. Until then, I'll live with the red light staring me in the eyeball.