Too much in the system will blow your compressor seal and you Will need a new one NEVER EVER!!!!! use the cans from the store you can not top off the system if your low it has to be evacuated and refilled by a skilled technician with an R-134A recovery/refill machine I know it's not cheap but you WILL damage your compressor by adding those cans. Also not trying to be a dick but it's either called refrigerant or R134a IT IS NOT Freon Freon was a pantented refrigerant made for fridges and freezers in the 80's. Sorry I've been an automotive HVAC technician for 6 years and those cans of "refrigerant" from the auto parts store cause more major A/C system failures than anything I can't count the amount of vehicles that I have to replace the compressor on to fix issues caused by somebody deciding to save some money And do his own re-charge you will spend about $150 on a system evacuation, pressure test, and recharge. Or spend $10 on those stupid cans and risk spending $800 on a new compressor and receiver/dryer. Sorry backyard mechanics but you can't afford the $10k machine needed toCORRECTLY service your vehicles A/C system just take it to the dealer or a certified an/c repair shop