This is not a job you can do yourself, even with the best of hand tools. First be aware refrigerant is extremely dangerous to work with. It can cause frostbite and blindness. Professionals wear gloves, safety glasses, and a face shield.
You need to recover the refrigerant currently in the system. That requires a special machine. Once the new compressor is installed, the system must be pumped into a vacuum to remove the air that got in, and more importantly, the humidity in that air. If any moisture remains in the system, it will combine with the refrigerant to form an acid that will attack the metal parts and corrode them. That will lead to expensive leaks. In the short-term, water circulating in the system will freeze at the orifice valve and block refrigerant flow. That will cause an intermittent loss of cooling that can last from twenty minutes to an hour until that ice melts.
Once the system has been in a vacuum for at least half an hour, the exact measured amount of refrigerant must be pumped in. If too much or too little is pumped in, it will change from a liquid to a vapor in the wrong place. Where it changes to a vapor is where it gets real cold, and you want that to be in the evaporator in the dash, not under the hood. You need another special charging station, and its vacuum pump to do that. The final step is to check the system for leaks.
If you replace the compressor yourself, then have your mechanic evacuate and charge the system, he is not responsible for any leaks or anything done incorrectly with the compressor. If there is a leak, he is obligated by law to suck the refrigerant back out, then you get to do the work over. You have removed him from any liability by doing the repairs yourself, and you will have to pay a second time to have the system charged. That is why this type of work is best left to the professionals. If they make a mistake, they have to correct it, but you do not get charged again for that work.
Saturday, June 24th, 2017 AT 9:45 PM