A/C Compressor short cycles after charge

I took my car to a mechanic to have the secondary cooling fan replaced. When he was looking at it, he said the A/C was low on freon and asked if I wanted it charged. I told him to go ahead. Well, the fan was replaced just fine. He put two cans of freon in the A/C, and when I got it home, I noticed that the compressor will only run for a couple of seconds at a time. It will run for the two seconds, then be off for a bit, then two seconds. It was working before it was charged. Did he overcharge it? He did say that there was a leak, but that he didn't know how bad.

If it was low there is a leak. Charging it may or may not help, obviously it is probably low again. Find the leak and fix it. Get the system vacuumed down and then have it charged and you should be back in business.

Since he put Freon in the car, that would suggest this car is older than a 1994 model year. Even then, 2 cans should be nearly the system capacity and if it were that low, I'd expect that the A/C clutch would not have engaged anyway. Was the vent temperature cold before you took it in for the fan work? Did he use a gauge set when charging the A/C or did he just connect a can with a single hose to the low pressure side and charge that way? How did he determine that it was low if the system was working fine when you took it in?

Even if the system is using R-134a two cans would be nearly the entire system capacity unless maybe the vehicle has rear A/C such as a minivan or SUV. If you have a car and he put two cans in without using a gauge set, you need to find a new shop to do your A/C work. R-134a systems usually will have a high and a low pressure switch. If they are undercharged or overcharged the compressor with cycle frequently or not run at all and obviously the comfort level inside the cabin will be impacted.

-Rod