Ok, after doing some more research, I found that the orifice near blower on left side is the low pressure and the one on right side is high pressure. From what I have seen, the low should be charged to 45 and high to like 275. Do I test them with engine on and ac running or when off? Also, how do I check the heater core to make sure that it is clean? Is it behind the glove box and accessed from cab or so I access it from under the hood? Dang manuals do not say.