What causes the heater to not be hot at idle. I get heat when I bring up the rpm's. Also how do I get the cabin filter to stop opening every couple of minutes?

 

Low coolant level may do that, or, an air bubble in the cooling system.

I don't quite understand the second problem.

 

I was under the impression these trucks didn't have cabin filters? And in my mind a filter, shouldn't open or close, just filter air. My wife's Buick has one for the heat and AC, and my grandfather's older BMW whateveritis has one too.

I wondering if he's talking about the blend door opening/closing?

 

Or the vents switching....

 

If you've got no air in the cooling system, then you've got a partially clogged heater core that's not allowing full fluid flow. If burping the system doesn't do the trick, backflushing the heater core, chemical cleaning, and more backflushing might fix it, might break it, might do nothing at all.