I have noticed recently, in this cold weather, that my power steering doesn't work well when I am stopped. It is fine if I am moving at all, but if I am stopped, it will assist when I turn the wheel just a bit, then it will feel like I have no power steering. To does this both ways, whether the truck is warm or cold. I checked the PS fluid, and it looks good. The PS belt looks fine, and there are no visible leaks. Any ideas on what this could be?

 

What type of fluid are you using in the PS pump? Should be Dexron III or the Dex/Merc equivalent.
Are the lines to the idle-up valve on the pump connected properly?