Was driving along with A/C blowing at high max when I lowered the blower motor speed and A/C temp went to outside air temp???What happened?.Noticed trucks temp gauge was at lowest point of gouge. on dashbd.
Not sure if this addresses your issue, but many GM products won’t turn on the A/C if the outside air is below a certain temperature. A failed ambient air temp sensor will cause the wrong outside temperature to be displayed and the A/C to be disabled.