Ok, So i was bored this afternoon and had some money to spend and decided I'd try and get the AC going on my 86 240 project, its not my daily driver yet but anyway, Ill get to the details.

I purchased an r12 to 134a conversion kit, and decided Id try charging my system. Well, apparently it had already been converted because the fitting that screws on was already there. so I hooked up the cheap little gauge and its super short hose to the fitting but there was absolutely no reading. Im a big rookie at this as my dad usually handles my AC components. anyway. So there was no reading on a gauge so i attached a can of 134a to the gauge, rotated it a bit and the gauge went up a bit so i saw it was working, so i went ahead and connected it to the fitting again, twisted the can as to let the refrigerant into the car, but nothing happened on gauge, i had the car idling and ac on full blast but absolutely nothing. shook the can, nothing.

any pointers, ive looked all over the past ac posts on here and have found nothing. what could be the deal?