1999 Chevy Suburban 1500May 5, 2014May 5, 2014I need to replace the low pressure switch on my AC system. Do I need to evacuate the coolant first before removing the old switch? Keywords:A/CChevylow pressure switchsuburban 1 thought on “1999 Chevy Suburban 1500” Freeautomechanic May 5, 2014 at 9:54 am Under normal circumstances, NO. You shouldn’t need to evacuate the system as there is a check valve similar to that on a tire valve stem just below the switch. In some cases this check valve can go bad and not do its job. In that case you would need to evacuate the AC system. Reference: http://www.freeautomechanic.com/airconditioning.html Comments are closed.