One more head light problem. 2005 Dodge ram 2500 5.9cummings. Every morning on a cold start my headlights will not come on when turning on the light switch. Also wiper, door locks, steering wheel controls, and turn signals don't function. I was thinking it might be the notorious FCM but if it was my thinking was that it would never work. After driving or leaving the car on for a while 15mins plus the light will work and everything functions properly. I am in So CAL so no cold weather issues here. Any pointers would be greatly appreciated.

 

Pull the fuse box and check all the electrical connections under the box for corrosion. While the fuse box is out you can remove the FCM and check it's connection also.

 

This may be a long shot. But, how are your batteries? I'm also in SoCal and when mine is cold (even with new batteries), the grid heater comes on and the wipers are VERY slow. I've never noticed the lights, locks, etc. If your batteries are low, maybe the grid heater is sucking all the juice while it's on .. after it turns off, everything works again. Possible? IDK. it's worth considering.

 

Some sick solid state electronic devices are sensitive to temperature.
If it's not bad connections then it's the FCM.