I checked the refrigerant level and it registered it was filled. I can see the compressor start and stop every 4 seconds. Why is this happening?

 

Hi Wilford,
Could you please explain how you determined the refrigerant level was correct ?

From what you have described the symptoms could indicate a possible low refrigerant charge. That is where the info you have provided is puzzling to me.
Can you help me out with some more info, thanks.

 

I bought a can of AC PRO. Instructions say to start truck, and turn on AC. Hook up the gauge that came with the can (without connecting the can yet) and read gauge. It said, FILLED.

 

I am sorry to say, this is very misleading.

To really determine if the system is fully charged a set of manifold gauges is required to get pressures within the system and based on those pressures , that are affected by temperature, is one way to determine if the system is charged with the right quantity of refrigerant and also by performance.

I hope you are protecting your eyes with safety goggles. Can you try to reconnect the can line to the low side connection , Let some of the AIR in the hose exit , then with all connections secureD safely, open the valve on the can and let some refrigerant go into the system. The engine has to be running and MAX air conditioning selected.
WHATEVER YOU DO DO NOT ALLOW THE CONTAINER TO TURN UPSIDE DOWN. THE LOW SIDE CONNECTION SHOULD ONLY RECEIVE GAS ,,,BUT NO LIQUID. IF THE CONTAINER GETS TURNED UPSIDE DOWN , THAT ALLOWS LIQUID TO GO INTO THE COMPRESSOR AND CAN DESTROY IT.

 

I'll try that and let you know. Thanks

 

What is the outside ambient temperature? If its low enough, the compressor might cycle. Even with gauges, if done incorrectly, air can be introduced into the system (suction side) via the long hoses. Overfilling the system is just a bad as an undercharged one.
If it is determined the level of refridgerant is low, that means you have a leak. That must be fixed or the refidgerant will leak out again, wasting your time.

 

Depending on how often you have to add refrigerant can help determine if you will ever find any leak without special leak finding equipment.

If you only need to add once a year, I would consider just adding it yearly and forget it until next year. If more often ,then it would pay to have a shop with the equipment check for where the leak is taking place and consider having it repaired.