Unit is running but compressor is short cycling and amping too high 15.5 amps full load is 6.5

Likely a bad run capacitor or needs a start capacitor. Or worse yet, drawing locked rotor amps and needs a new compressor.

You didn't provide all pertinent info available to you. Lets take what we have; and, consider why your compressor is overloading the circuit breaker. Points to ponder:

1. Not knowing the exact model (not series) I don't know what the amperage pull is for your "extreme" compressor or the circuit breaker's rating. A 25 amp compressor connected to a 25 amp breaker could be an issue. Campbell Hausfeld's support pages are crashing so I can't check the possabilites.
   

2. Are you using a lightweight extension cord? The lower the rating of an extension cord the higher the amp pull on the breaker. If you eliminate the extension cord does the problem go away? Ohm's Law applies. <http://www.ohmslawcalculator.com/ohms-law-calculator>
   

3. What else is on this breaker? Is there other high-amp equipment in another room (water cooler, window air-conditioner, portable electric heater, etc.) pulling from this same circuit breaker.
   

4. Is the circuit breaker not performing to specification? I've seen failing breakers trip early.
   

   First, check the owner's manual for power requirements. Next step, use no extension cord; and, insure nothing else is pulling power on that breaker. Then, use a different breaker and see if the problem follows the compressor. If all else checks out than I'd consider binding in the compressor causing the amp pull to be too high.
   

   Good Luck!
   

Are you heating or cooling? When the outdoor unit shuts off how does it come back on. Or are you saying that the outdoor unit is short cycling off and on

The way I check compressor problems is : If it kicks off on the overload , remove the overload / relay . Check all 3 terminals with the meter set on beep . Also , check each terminal to any part of the copper compressor lines . A beep there would indicate a shorted compressor . I would then replace the overload / relay ( wiring correctly with the capacitor ) and connect an amp meter to the overload wire . Plug in the refrig and check the compressor run amps . New compressors usually run 0.7 amps . If the compressor runs anywhere above 2.5 amps , then a lot of wear is on it and not much longer life . I never use a 3 in 1 due to these are only a partial fix and will not last long . Actually , If a refrig comes into the shop , these are jerked off the compressor and thrown away . I consider 3 in 1 absolute junk and frown on any technician using them . Refrigerators come to our shop ( we pick up from lowes , home depot trade ins ) and I've thrown many away , which also means they cannot be permanently used .

Compressor LRA ( locked rotor amps)meaning that if you hold that rotor and do not allow it to turn, it would draw that many amps.
Compressor RLA (rated load amps) meaning the amps the compressor will draw at a certain outdoor temperature usssually 95°.
Fan FLA (Full load amps) meaning that's the maximum amps the motor will run at continuosly.

If this is aheat pump or reverse cycle unit that amps in heating is to high. Should not go over nameplate amps in heat or cool. Sounds like maybe two things. Overcharge and stopped up coil on the inside air handler. The reason for the high amps is in heat the head pressure is higher than normal. So check the coil inside and have the charge checked because that compressor wont run long pulling that much amps over nameplate. Keep in touvh Rus.

a full size refrige has to be on a 20 amp circuit, a 15 amp is just not big enough.. you should also know that this circuit has to be on a 12-2 gauge wire.. I also highly recommend installing a 20 amp HD receptacle

Short cycling of the compressor can be an inconsistent cause of a breaker overload. It happens when the compressor start winding is "jolted" into operation several times over a short period this can happen when there is a loose power or control wire connection that is broken from the vibration at start up of the compressor or by the occasional "jiggling" of the mercury in older analog thermostats. I suggest that all electrical connections are checked and that you use a newer model thermostat, if its not already that has a built in start delay circuit.

Hope this helps you if your still having trouble with this issue.

I changed out the startup and run capacitors. A/C runs fine now

Most likely a bad compressor. You could try a new relay on it first.