79  low pressure on high side a/c com   30 lbs on low side    low pressure on high side the this mean bad com ? just asking   david

It could mean the system charge is low also. I would try first to add one can of freon to see if you can get that high pressure up. You need to make sure that you're adding the same type of freon that's in the system however.

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1973 L-82 4 spd