I'm recharging the A/C on my truck when it occurs to me that the gauge on the recharge kit red lines at about 70 psi, but the gauge continues on up too 200 psi. So this leads me to believe that the 70 mark is just some safe generic number. So what is the maximum pressure that our system takes?

 

That type of setup is used only on low pressure side. The pressure for the low side when correct will cycle the clutch on at 40 psi and off at 23 psi. You should not see 70 unless the ac is off. And by the way, add 134 with the valve up (gas)

 

Generally systems are charged in weight of refrigerant, or lbs. So yes 70 PSI is just some generic number, but its not much lower then what it should have. Charge it up to 70 PSI anyways and with the AC on the coldest setting, fan on max, and it set to fresh air (may be "Normal AC" on some vehicles, as opposed to "Max AC" which recirculates air) the air coming out of the vents should be about 40*F, and when the compressor cycles on, it should stay on for 30 seconds or more before cycling back off. If it goes on/off every few seconds then you need a bit more refrigerant. Make sure you fill with the AC OFF, and give it about 30 seconds or so to equalize before you go to fill it

Its also very important to note if the system was working at all. If there was not one trace of cold air at all, then there is a 90% chance all the refrigerant has leaked out, and atmospheric air and water vapor has entered the system, which is very very bad for air conditioning systems and can cause premature failure of the compressor. If there was no cold air at all, you are going to need to bring your truck to a garage so they can properly put the system in a vacuum and recharge it.

 

It works fine I guess, I just wanted colder air. It just isn't as cold as my cousin's 97. I thought perhaps I was under charging the system. Thanks for the help.