i added one earlier without the gauge so i don't know if it is still empty. ac is working below normal, so i was wondering adding another can of that, that comes with attached gauge so i can monitor that it is filled or not.

but problem is that they are from different company, so is it ok mix them?

 

Maikal, when you say R-134a, it is the same chemical. So, whether you are adding it all from 1 manufacturer or from 5 different ones, it doesn't matter. Now, with that being said, some will add oil to the freon, others won't. So, make sure that when you are adding more freon, you get the stuff with the oil added in already to make your life easier.

On a side note, make sure you are not over charging the A/C system as this can lead to expensive repair bills. Besides, if you are having to add that much freon, you have a leak somewhere and odds are, you will just be dumping more money down the drain until you fix the leak (the freon is just going to leak back out on you). Not to mention that an A/C system needs to have all the air removed from it for it to work efficiently. If you let all the freon leak out, odds are, you have air in the system and no amount of freon you add is going to get it cold like you are after.