While driving the A/C blows cold but when idling it gets warm. What would cause this and how do i fix it?

Chris

 

Probably a little low on freon.

 

Its the new freon not the 12. How hard is it for a novice to add or should I just have someone do it?

Chris

 

I would put a set of quality gauges on it first to make sure that is the problem. Adding 12 oz would not be hard but you need to make sure that is the problem.

 

R134 does not cool nearly as well at idle as did R12, but not much can be done about that.
Your vent and fan controls, if vent is open and letting in outside air, this doesn't help, run at Max AC for vents to be closed, helps some.

Don't start adding refrigerant without knowing how much is in it already and what max capacity is. Can blow the lines and run up a good bill.