A/C trouble 2010 lariat
 

well now that the weather is warming up ive found out my a/c doesnt work very well. the air is cool but far short of COLD. at first i thought it might be low on r134, but now i dont think so. i hooked up the gauges(high, and low). added about half a can of r134. but no differance. 80 degrees outside low side pressure 25, high side pressure 230-250. adding r134 didnt raise the low side at all, just the high side. low side pulls down to 25 and after about 20-30 seconds there the compressor shuts off and then cycles again.

it sounds to me like expansion valve but id like any other opinions. i bought the truck in february so i dont know whether the a/c worked last year or not.
also where is the expansion valve located at? its not under the hood.
thanks for any help

My 2010 has had AC issues in hot weather from day one. The AC operation is tied into the PCM. Best fix for mine was a second PCM reflash (10-13-5) for cooling fan strategy. Still takes forever to cool down the cab, but the discharge air temperature decreased by five degrees after the reflash. As long as I don't have to ride in the back seat, I can live with it.