HI ..ric here....
I have a 2010 ford flex with regular air, not dual climate control. For last few weeks a/c blows cold at idle..but as soon as we go into the texas sun..and ambient temperature rises..ac does not blow cold.
I have done the following:
Purged old freon. Applied negative suction to -5 psi for 20 minutes,..recharged with 134a and noted low side at 50 when ambient temperature at 90 degrees outside.
I changed out the evaporator ambient air temp sensor ..a new black one..and this did not correct the problem. Both a/c and coolant fans running upon turning a/c on. I now see where there is a pcm reprogram release ids 56.12 or higher.
Is there something else that causes the air to not work efficiently and is causing it to be highly variable in its reliabilty a few minutes after startup ,..it almost feels like a vacuum cutout of the air as was common on vehicles when in passing or kickdown mode....any iedas after all these things have already been done? is there a thermal expansion valve or some other sensor that i should know about?