Refill Air Conditioning from 18 ounce can
 

Not sure what forum to ask this on.

This is an after market 134 system in an older street rod. It has a small leak evidently as it needs topped off about once a season.

I see the cans of 134 freon for sale at $25-$35 at the parts stores and Walmart. If you follow the instructions is this an OK method to use or not?

They say they have oil and leak stop in them too.

Most retail places want $100 to do it.

The correct charge of 134a is a lot more critical then the R12 used to be. 134a has higher operating pressures and you can damage the compressor with a relative small overcharge. Most factory 134a systems have a high pressure compressor cut off but a lot of the add on type don't. System performance will drop with a small overcharge also. I repaired one last week that wasn't cooling well for a reason other than low refrigerant but before the guy brought it to me his son had added 1.5 lbs. which is exactly how much it was overcharged. Had to correct that then fix the 1st problem. I wouldn't recommend charging anything without gauges and watching the pressures. I definitely would not use stop leak. It never stops leaks and just causes other problems and can damage A/C charging equipment. If you're not properly equipped to do this job it will end up costing you more trying to do it yourself.