Did I overcharge my cars AC?

I like your name, haven't seen Young Frankenstein in a while.

Your a/c system must have been completely empty. You do not have enough in the system. You could probably add two more 12 oz cans to fill it up but you really should take it in to fix the leak. Otherwise, the freon is going to leak out anyway. And I doubt you added a can of freon with oil to replace what you have lost.

Sounds like it still may be undercharged. Or the relay switch is bad. With out a gauge no one can tell. But if you have a thermometer. Once it is charged you set it in the vent. Air on and if it drops to 55-52 F you have the right amount in it. They work backwards over charge and they will run warm. Under charge and they will run cold. I would try a fresh can. And add more to it. It still clicks on and of. Replace the relay switch. Usually a can will not over fill them.

I always suggest when it comes to adding freon gas in your a/c system, let an a/c technician to this for you. Its not like adding oil in your car. Adding freon gas requires accurate amount of freon so that your a/c system will function properly. Putting to much could break your a/c compressor and will not give you a cool air likewise putting less will not also give cool air. I suggest to bring it to an a/c technician to check your freon gas level using gauge. Hope this help!

first check / adjust thermostat setting if available , "the blue and red knob"

place it somewhere in the middle, when aircon works normally, compressor will turn off and on depending on thermostat setting or how cold you set the thermostat,

in case that you have the correct setting and you still experience the on-off-on-off of your compressor,

better check /replace expansion valve on you evaporator assy, then refill freon according to specified amount..

on-off-on-off reaction in a very short interval specially when engine at idle or when you release gas pedal after revving, it is most likely that your expansion valve in clogged.

Was the R134 recommended for your car? you can't over fill the compressor it automatically stop when the compressor is full.

If you don't have enough freon it will cause your AC compressor to cycle on and off and on and off and on and off.... get a cheap guage from Orielly and see how much freon you have...