Three weeks ago my 99 F-150, 4.6l, 4x4 with 50K would not turn over. When you turned the key there would be a single click under the dash and all of the lights would dim completely out. (sounds like a complete drain on the electrical circuit) The starter would not make a noise. When it warms up above 15 to 20 degrees, it starts fine, like nothing is wrong. I put in a new battery and that worked for a day, probably because it was in the garage and warmed up, until it got cold and then the same thing. I left it at the local garage when it was very cold. It would not start for them. They checked the electrical equipment and said the celinoid in the starter was freezing up. They put in a new starter and it worked for three weeks. It has been in the single digits at night and I thought everything was fine. Yesterday morning it would not start, it has been in the single digits for a few days in a row and cant figure out why it waited until now. In the afternoon it warmed up to 20 degrees and I went out and it started. This has me very concerned. Can I leave the house and if it gets cold will I be able to get it started again. The garage is going to look into any info they can get from their sources. The key turns, and it draws the current, it has to be something that is stoppping the current from getting to the starter, and it has to be with very cold temps. Maybe a computer chip?
Anyone have any ideas?

 

Another idea is that it might be the starter relay? Anyone have a best guess?

 

My initial reaction is to suspect the ignition coil, but I don't think the cold would make a difference in that. It should either work or not work.