Just read a thread where flintknapper suggested putting first can of Freon in the high side port with vehicle and ac off. This is a 2005 Expedition that I just replaced the compressor and drier in. Pulled vacuum to -28 and it held that for 5 hours. When I tried to get the Freon in the low side it wouldn't take it. The clutch won't engage of course with no Freon. That is why I am hoping to get clarification if it's ok to close the low side on my gauges and put the first can in the high side. Thank you, William