3.42 pounds+- .05 4.5 cans is a safe maximum. The sight glass will still show bubbles with r134a when fully charged. You have to go by volume not the sightglass when charging with 134. If you actually pulled down to 29 inches vacum which is highly doubtful... most likely gauge error but even so if you pulled down close then the first can will be sucked in entirely by the vacum in the system. The next can will be close. Are you sure you're feeding it into the low pressure line and not the high pressure side? The larger diameter line is the one you want to tap into the schraeder valve on.
I think on the 525 its the lower line not the upper... The sightglass is on the high pressure line, you don't tap into that one. At any rate, you fed 2.5 cans in and now with the engine running and the ac turned on maximum cold you feed the rest in. IF you're on the right line and everything else is correct it will pull it in slowly, holding the engine at a higher idle helps too.
If you still can't get it all to go then you have to get a pan of very hot water and stick the can of 134 in it to heat it up and raise the pressure so it will be higher than the system pressure and go in. The water will chill down very quickly doing this so you may have to get more than one pot of hot water. Don't submerge the tap on the can just most of the can itself.
I strongly suspect you're using the high side line instead of the low side but if not then you can also check fittings where you're gauges screw onto the schrader and onto the can tap sometimes if those are overtightened the oring seal squiches and won't let gas flow .




Quote Originally Posted by glen-sj
The R134a cans are 12 oz, so doing the math would need 4.5 cans of R134a. The problem is the system will not take anymore after 2.5 cans. There is still a steady stream of bubble in the sight glass and warm air from the vents.