With all the threads a while back about the fast idle, my is enabled. This past week here in North Carolina has just brought winter. I did notice this week while leaving my CTD running for short periods while running into a couple of shopping places, with the fast idle OFF, the CTD would automatically increase the idle rpm for a very short time and then would slow down. It must be sensing the temp outside as below freezing. Is this Dodge design or my TST? You guys noticed this?

Yes, this is normal. I noticed the same thing with my truck when the cold weather came to KY a couple of months ago. Truck is bone stock so it is a gift from Mopar.

Yes it is normal. Based on outside air temperature and engine coolant temperature your truck will idle up to 1000 rpm's and once engine coolant is warm enough it will idle back down. Your truck has to sit in park with foot off brake for 2 minutes before it will idle up. Mine lately idle's on 1000 rpm's steady (temps below zero lately) Throws heat much better than my gm did!

The trucks will do it automatically on outside temp. However, you can have it enabled where you can make it happen for those mornings that are not cold enough for the truck to decide to do it. You can go as high as 1500 rpms. If you had a pto on the truck that would quite useful.

Up here seems like 1000 rpms isnt enough to keep up with the heat loss. Need 1200.

Yes my dodge 2500 does the same thing ging from 750-1000 up and down... my trucks first winter too...lol..... i guess it is normal