2001 Olds silouhette premiere van. dual ac left and right climate control. Evac’d and recharged twice recently. Checked for leak was negative. AC blows super cold except on highway where it goes from cold to hot and back randomly.No problen in city.
Who is doing the work. If it is the dealer or the local quick lube place, That is the problem. You local AC shop (in the south or your local radiator shop (in the north) should be abel to straighten it out.
I agree with Joseph.
I posted a link to information about automotive AC systems.
http://www.familycar.com/Classroom/ac1.htm
It sounds like your problem may lie in erratic operation of the expansion valve (or orafice tube) that controls release of the refrigerant to the low side, where it chills the evaporator core. But it’ll take an AC pro on-site to truely diagnose and repair it.