i would like to know what controls the heater grid, like at what temp to come on, and how long to stay on. My wait to start light stays on longer sometimes than otheir times, when the truck sits all day at work the light may go out like the engine was just run in the past 30min. and when the truck starts its not a clean crisp start. When the light stays on fore awhile like it should when the engine is cold it has a crisp start.

 

Sounds like it is working alright to me.

 

I tried looking it up in the FSM, but it doesn't give any operating parameters, just wiring diagrams and remove/replace instructions. For the actual scheme of how it operates it refers to the Powertrain Diagnostic manual, which I don't have. Like BigBlue said, though, that's about the way mine operates too, so I think what you're seeing is normal.