A/C Problem. HELP!

your condenser is plugged up with dirt. take compressed air gun and blow from the motor side of the radiator thru cac and condenser. You will need to work the corners extra good you are not getting enough air thru the condenser to change the state of the freon thus high pressure and burning up the compressor

 

I have a 1998 Freightliner classic. I have replaced everything on the AC . New compressor, new hose, new lines all the way to the bunk. I have replaced the dryer and expansion valves and the evaporator core. Problem I'm having is once it's charged up by the mechanics everything appears to be working yet it blows warm out into the cab and bunk. I'm at my wit's end. What an I missing. Have replaced high low switches. Only thing I've yet to do is replace the control panel and tear down the dash to see if the air operated doors are working properly. Would appreciate any advice.

 

Only things left are condensor and expansion valves. Condenser and radiator need to be clear of debris. Refrigerant charge is 3.7 lbs. or 55 Oz. I usually put 5 cans, Purging each can of air in the attached hose, before adding it to the system. If it hasn’t already been done. Take condenser off. Easier if you can take the grill out first. Leave lines hooked up. Clean the fins, on the condenser and radiator, so the fan can pull air through it when engaged. Assuming you put the right amount of oil and refrigerant, and condensor and radiators clear, the condenser itself may be plugged up with trash, from past failures, There’s no way to flush them, since it’s not a closed loop.They should be replaced, after a compressor fails, along with flushing the lines. Other thing it could be, is expansion valves. It’s possible that both are blocked, and sticking. If so,sometime the evaporators will ice over, by turning the a/c off for a few minutes they’ll thaw out, and system will work again, till they ice over. First thing I would check, is the operation of compressor, and fan at an idle. Compressor should kick of, and fan should kick on,till condenser cools down. Then fan kicks off, compressor kicks on. On a hot humid day, compressor should always run longer than not, about twice as long seems about right. Blocked air flow, or Too much Freon will make it cycle off, due to high pressure. Sometimes just a little bit too much makes all the difference. When adding or removing Freon, a little bit at a time, give it time to cycle through. My guess is you have either too much, or not enough Freon. Too little, compressor runs all the time. Too much, cycles off too much, staying off too long, and too much can cause the evaporators to ice over. Moisture in the system, can also cause the expansion valves to freeze up and stick. A new air drier is a must, and a vacuum of the system before re filling is always best, to eliminate moisture.