No you just refill sytem but would need gauges to see when its full or a sight glass in sytem and when the sight glass is clear not showing any bubbles it will be full......with ac on
Make sure you refill in on the low side and not the high side of sytem ...look for connection where the pipes are larger or near the accumulator ................be sure not to mix r134 with r12 freon .............
bg
March 2009