hello everyone , I need a little help with a/c. I had added some refrigerant a couple weeks ago because it wasn't cooling very well . now it blows colder at idle vs. driving at highway speeds.
I was going to evacuate the system and vaccum it down then recharge it. . my question is once I vacuum it down and recharge the system , will I need to add oil to the system .
placard on fan shroud says it take 2.83 lb of refrigerant and 9oz oil. btw the truck is a 07 f-250 lariat cc with 6.0 .
thanks .

 

Your oil charge will remain with a proper evacuation. Make sure while you have the system down to replace the orifice tube.

 

I'd put gauges on it and see what the pressures are doing. If at high idle it is short cycling then you may just need a little more if the low pressure is dropping out, OR you're a little over filled and it is over pressurizing on the high side and cutting out.

 

thanks for the help guys , I took your advice ford390gashog and changed the orifice tube .when I pulled the old one out it was totally clogged.

 

You are going to want to replace your accumulator.... That is where that stuff usually comes from.... They are pretty cheap.

Richard