Some background...I teach HVACR at College here and also am the HVAC program director. So, it is not low on charge. AC is still ice cold when moving slow or fast, not blowing cold at stop or idle...doesn't matter. Fan is never moving when idling, that's why I suspect bad fan clutch and I also read that an auxiliary electric fan aids in cooling and performance increases as well. Not thinking vac leak because engine runs smooth, rpm is constant and there are no other indicators pointing to that being an issue. Tensioner pulley, belt, everything in perfect synch...no belt slippage at all.
Coolant levels perfect, never overheats. The compressor is not turned with every rotation of the engine when the ac is not engaged, if it did gas mileage would be horrendous,so the ac on any vehicle has to be turned on 1st.
Thanks to everyone for their suggestions. I'll let you know how it worked out after I install the new electric fan on Friday.

 

Fully believe its your compressor . Why? whats the only thing that changes between idle and driving? engine RPM! what is effected by engine RPM? the a/c compressor Test it by not letting it idle at a stoplight! put it in neutral and keep it at about 1600 RPM

 

PROBLEM SOLVED

I feel kinda dumb at the moment. Ol' grouch hit the nail on the head. I looked at it again. Of course, I knew the fan was not spinning at idle. OK, so I 'assumed' it was spinning while moving, and I'm pretty sure it was for awhile. I went to the store today (2 miles there, 2 miles back) and when I got home, coolant was bubbling and truck was overheating....hmmmmm... I let it cool down, had lunch, went back out. I noticed black fan shroud material on the tip of the fan blades. Awww crap, fan doesn't turn now....started it up, it was stuck on the shroud. Grabbed the shroud, bent it back up away from the fan (heard the plastic crack a bit) then tried to spin the fan...and...just like that, it turned. So I start the truck up.....and....just like that...as soon as it started, the fan went on....and stayed on. The ac got cold...and stayed cold. Just like in the movie I thought I heard Major Payne say to me...."Who's the dummy now? Heh Heh" Thanks to everyone who responded.
NOW...what to do with the electric fan I ordered online and haven't received yet. Fortunately, it was only 18 bucks (yeah, I'm a cheapskate).

 

I'd laugh and point a finger if I hadn't done similar things in the past. If you've never make a mistake, you've never make a discovery. I've made LOTS of discoveries in my life.

I'm wondering why it was stuck in the shroud. Has the engine shifted? Truck bumped in the front end? Water pump going out? Done some work and got it back on crooked?

As for being cheap, my next wallet is going to be a Scottish wallet. Held closed with velcro so when I try to spend a dollar it's scream in agony. I'm sure you'll find a use for it eventually.

 

Good point. I did watch the fans rotation, no wobble at all....last week I kinda messed with the shroud by popping the plastic pins to lift it up and away to get a closer look at the radiator etc. I bet that when I popped it back down I must have pressed it down at an angle,just enough to lock in the pins but perhaps the front pins didn't seat right and left the shroud at an angle, just enough to stop/slow the fan....Kile I said...felling like a dumb *** about now. AND,I wasted all you guys time.

 

Nope...I just learned something from hearing your experience.

 

You aren't wasting our time. Face it, if we had something constructive to do, we'd be doing it. Besides, people reading this will have an idea of what to look for in the future. You will also have a reputation of being knowledgeable later on when you see a similar problem crop up. I think you said you teach HVAC or something. Now, your students will be amazed at your wisdom. Wisdom is gained just AFTER you needed it in the first place.