- High pressure shut-off switch - Clutch cycling switches must be adjusted or replaced when retrofitting from R12 to R134a. - FJC has a full line of switches specifically designed for R12 conversions. For use on systems which have been retrofitted from R12 to R134a. - Replaces R12 cycling pressure switches. - When retrofitting these switches have a lower cycle off pressure to compensate for pressure differences between R12 and R134a - Use these switches as instructed by the "Guide to Retrofitting" Manual.