[EC900]

I used a DYI kit, AC Pro on a 20 yr old BMW and had good and quick success, even fixing an internal seal leak that contributed to the 134 loss after sitting for 2 years. I applaud your tenacity and willingness to get the tools to fix the system. But I think you answered your own concern - DYI didn’t yield a satisfactory result.

However easy these DYI ac recharge kits are, there are other things to consider like the pressures High and Low balance. The AC Pro and maybe the others only add to the Low side, even their connector is foolproof but it doesn’t account for or measure the pressure on the High side, which might be the reason your popped the relief valve. Too much on either side (H/L) will affect any ac system even on an otherwise working system, I don’t think or know if the DYI kits are intended for Full charge, but only to ”top-off” existing refrigerants, then and especially on an old unused system that likely has deteriorated seals and perhaps corroded aluminum lines or fittings could be a waste. An ac shop can pressurize the system and indicate maybe even locate leaks w/o using refrigerants and that would be the route I’d take but really, but anything over 40 yrs old is destined to have costly items to replace piece by piece going forward and that’s where I would draw the line and surrender to fix an oem ac system.