AC not cooling. Replaced compressor, flushed all lines separately, flushed condenser, flushed evaporator, ran vacuum pump for 3 hours, held vacuum, so no leaks. Replaced expansion valve, converter to 134. Replaced all vacuum lines in the engine compartment and confirmed all actuators and shutters work as designed when AC is selected on dash. Inlet tube behind expansion valve going into evaporator gets ice cold with visible frost and low side port gets real hot. All this and pumping 80 degrees through vents. What have I missed?
Hello John –
It sounds like you have done major work on the refrigeration system on that 1965 Lincoln. I assume that you have also replaced the receiver/drier and have the correct charge of 134 refrigerant and decent pressures. The thermostatic cooling clutch unit and cooling fan must also be correct and operative. Because these Lincolns of ours are luxury cars, the controls are fancy and mostly complicated, therefore use of the Factory Service Manual is usually an important necessity for any diagnosis and understanding the system. These systems work very well when all is in good operating order. It is possible that the control system in yours has a problem, therefore I can make the following suggestions. For maximum cooling in very hot weather the compressor will not usually cycle. If it is, the compressor clutch circuit should be inspected as per the manual. The water valve may be inoperative or receiving the wrong vacuum , bypassing the valve internally or an incorrect valve. If it is in fact not closing when it should or is bypassing internally it could be reheating the refrigerated air somewhat before it is discharged into the vehicle interior. We use a simple test to find out if this is happening. The rubber heater hose near the water valve can be temporarily clamped shut with a gentle clamp that you can easily make up at your shop. If this clamping makes the cold air outlets much cooler when the system is tested again you probably have located the problem. The above are only two suggestions of problems that we see at Lincoln Land quite often. If you do not have the proper Service Manual and would like one, please call George or your Parts Contact here at Lincoln Land.
We wish you a speedy diagnosis and please let us know what you do find or if you need further advice or parts.
I did not replace the Drier, but have one on its way and will replace this weekend.
Based on R12 to R134a calc, I used 36 ounces of 134a to refill an empty system. Is that correct? The book calls for 2.5 lbs of R12, so 90% of that is 2.25 lbs or 36 ounces. In regard to my pressures, my ambient pressure seems to be okay – both sides at about 110 after sitting without the car running. The problem occurs when I put the AC on and I have a negative value (pulling vacuum) on the low side and about 150 on the high side.
Thermostatic cooling clutch unit and cooling fan are both correct and in good order.
New compressor and clutch and both seem to be working fine.
I did have a leak in my heater core, so I bypassed the entire heating operation a year ago. No coolant runs through the system at all.
After reading your response to our earlier reply it is clear that a major error was made in not replacing the receiver drier with a new one at the time of the flushing and compressor replacement. I do hope also that your flushing of the condenser and the evaporator was successful and that the compressor that you used was new, properly rebuilt or a known good one. When you replace the receiver drier this weekend you must at this time also remove and inspect your new expansion valve for fresh debris lodged inside the valve. I am assuming that this valve was a “new” one recently and not a used one. Your refrigerant charge appears to be correct and I assume that you have the correct amount of oil in the compressor.
Erik my co-worker here at Lincoln Land advises to also inspect any of the “quick connect” refrigerant lines that may still be on the system under the hood. These original lines are known to plug up at the connection or fail internally in a way that causes a serious restriction. We wish you success this weekend with the drier replacement etc. and that you finish off with a real COOL Lincoln.
Appreciate the additional reply. I think I’m getting to the root cause. I’ve pulled it all apart and flushed each system and line individually and found a bunch of gunk throughout. I removed the dryer and will be installing the new one, putting everything back together, and vacuum pumping it over night. Two questions, is it possible that the crap from the dryer is in the compressor? If it is, should I drain all the oil and replace? Also, the manual calls for 9 ounces of oil, but that is original and for an R12 system. Is that the correct amount for this system with 134 and a new York style compressor?
When a/c equipped cars sit unused for many months and sometimes many decades the refrigerant in most cases leaks out. The system then begins to deteriorate internally and break down. Internal parts of the drier then migrate through the system when the compressor is started at a later date. Because flushing the condenser and the evaporator etc. is no guarantee of a clean system, we at Lincoln Land advise that these components be replaced with new parts along with a new receiver/drier and expansion valve. This assures us and the customer that the car will not need to return any time soon for any a/c work. If the car owner decides to “take a chance” and to go with used parts of unknown condition or flushed out parts, that is his decision that we will respect during the repair.
If your evaporator and expansion valve were loaded with debris again, I certainly would consider flushing the compressor and using new oil. Did you ask your compressor supplier how much oil is needed?
Thanks again Bill. Your knowledge has helped me tremendously. I cleared everything out and put the new dryer in and vacuumed the system earlier today. I’m blowing nice cold air once again.
Thanks again for your help and have a great long weekend.