AC Compressor clutch locked up-how to check if metal is in the system?

Had the bearing go out on the beater truck last week, same thing happened, froze and destroyed the belt.

$40 for the bearing and it took 35 minutes to change out because of the yapping mechanic.

 

The new compressor has oil in it already. About enough for the whole system. At least 4-5 oz. maybe more. Not sure. When a system gets a leak, most the oil settles and stays in the system. Especially in the condenser and evaporators. When replacing any component, the right amount of oil can be a guessing game. They suggest draining the old compressor, by removing the black drain plug, measuring the oil. Drain the new compressor and only add back the same amount that the old compressor had, plus 1 oz., because 1oz. will remain in the old compressor. That’s assuming some of the old oil is still in the system. There’s other guidelines. For example if you replace or flush just the lines, ( maybe add 1 oz.) I can’t remember the exact numbers. It goes on for replacing condenser, evaporator, These are best guess guidelines. Not exact. Unless you flush the whole system, replace the evaporator, condenser, or at least try to flush with pressure. It’s impossible to get the exact amount needed. Sanden suggests when oil amounts are in question, that less is better. The reason being, that too much oil displaces refrigerant. A/C might not work as well. More importantly and the real concern is, because the compressor itself relies on refrigerant for cooling. Too much oil will cause it to run hot, and actually shorten the life of the compressor bearings. Before learning this, I’ve replaced compressors as is, full of whatever oil was in them. They worked fine. I’ve even wrongly added more oil and less refrigerant. I thought it would help prolong the bearings, and was a small trade off. That was totally wrong. Pretty sure the suggested ratio is 7% oil. On a Freightliner, that’s about 4 oz. for the whole system. After getting the compressor oil level correct, I wouldn’t add more than 1oz. to cover any oil lost from the lines. Another mistake I used to make, was not fully charging the system. Less pressure, good. Wrong. The compressor just runs longer, and won’t work correctly on real hot days. Very important to put the correct amount. Don’t make that mistake. Lot of people do that, because it’s blowing cold, and being afraid of overcharging the system, blowing out a component. You need that full amount, especially on hot days. If for some reason you do over fill the system, you’ll know, because the high pressure switch will shut it off, and it will start short cycling, before blowing a hose. Last thing to mention is the one I always forget to do. Put a socket or wrench on the center bolt of the clutch, and turn the compressor 10 revolutions by hand before charging the system. This is suggested to lubricant the bearings, and avoid a sudden dry start when charging. Good luck.

 

The Low pressure switch should have wires 77P and 77E going to it. High pressure switch will have 77N and 77J.