2009 XLT will not take A/C charge

[Run Amok]

The A/C blows out lukewarm or barely cool air in my 2009 XLT with 4.0. Bought a couple of cans of refrigerant/leak sealer but the vehicle doesn't seem to take any and the cans do not appear to have discharged much, if any refrigerant. I'm using the low pressure side to add the stuff. But the gauge doesn't seem to change. It runs up about 2/3 of the way into the green zone (I forgot how many PSI it was) and then when the compressor clicks on it drops down to about halfway into the white or low zone. It just keeps going back and forth to the same locations when the compressor clicks on or off.

 

[Rick]

Fill a bucket with hot water and place the can in the bucket while filling. Just make sure to keep the can upright.

 

[Run Amok]

Fill a bucket with hot water and place the can in the bucket while filling. Just make sure to keep the can upright.

Thanks Rick. Doesn't cost anything, certainly worth a shot.

 

[Run Amok]

I'll be taking it in to an independent shop next week. Over the phone the guy was up front and said that he probably couldn't help because if he had to evacuate the system it probably has sealer in it, which gums up his machine and he doesn't want to do. Can't blame him for that.
But he's willing to look at it and says he won't charge anything if it's something he can't address.

 

[Run Amok]

Got it to the guy mentioned in the above post and it was fixed within a couple of hours. Turns out that there was somehow air in the system that wouldn't allow refrigerant to be introduced. Purged, charged and leak tested twice. One time for 30 minutes, another for 25 minutes. Ice cold now. $280 fix.
He seems to think it could be due to an old front end hit where the condenser was replaced and no one ever recharged the system. Something that I was not aware of and did not show up on Carfax.
Or another possibility that I'd overlooked and forgot to tell him about. Had head gaskets replaced a few months ago. Not sure if A/C lines had been unhooked, refrigerant lost and then air entered the system when the lines were off and I was not informed of this.
I bought the vehicle last October so had never tried the A/C to know if it worked or not before the head gasket job.