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1990 Dodge D250 Cummins A/C Compressor
Posted: Tue Apr 14, 2020 7:33 pm
by edahall
I installed a new A/C compressor in my truck about a year ago. Unfortunately, the cooling performance was much reduced compared to the original compressor. Today, I installed a new parallel flow condenser hoping that I could get better cooling performance. As I was charging up the system and cold air was just beginning to come out of the vents, I started to hear something squeal. By the time I figured out what was squealing, the compressor completely locked up. The clutch is free but the compressor is completely locked up. It cannot be turned by hand. What's going on?
Re: 1990 Dodge D250 Cummins A/C Compressor
Posted: Tue Apr 14, 2020 8:16 pm
by Tim
Sounds like you already know the answer. Many questions could be asked, oil amount, refrigerant amount, low/high side readings. If pulley turns and hub of the compressor is locked. Time for some more parts.
Re: 1990 Dodge D250 Cummins A/C Compressor
Posted: Thu Apr 16, 2020 6:43 am
by edahall
After removing the compressor that locked up, is there a way to tell whether or not it sent debris throughout the system? I had just installed a new condenser and I'm hoping I don't have to replace it again.
Re: 1990 Dodge D250 Cummins A/C Compressor
Posted: Thu Apr 16, 2020 8:58 am
by Tim
Drain and check compressor oil. Can also cut open the drier.
Re: 1990 Dodge D250 Cummins A/C Compressor
Posted: Sun Apr 19, 2020 2:59 pm
by edahall
From what I understand, there has to be enough charge for oil to circulate through the system. If that is true, what keeps a pump lubricated when the system is being re-charged?
When I was re-charging the system after replacing the condenser, the compressor was sucking in the freon slower than molasses. I was about 45 minutes into it when the pump locked up. When I removed the pump, it was bone dry! Since then, I have installed a new pump and cooling performance is much improved.
Re: 1990 Dodge D250 Cummins A/C Compressor
Posted: Sun Apr 19, 2020 4:18 pm
by Tim
Al9 wrote:Unless you have a sump (and your compressor doesn't feature neither a sump, nor an isolated crankcase that can store a good amount of oil), almost nothing keeps the compressor lubricated during a DIY recharge accomplished with the compressor on, except perhaps that little oil (usually half an oz) which manages to cling to the metal due to polarity (PAG and POE oils are both polar lubes). A really low refrigerant charge can prevent any oil that leaves the compressor from making its way back home. Compressors are usually made to withstand some serious abuse, but they aren't immortal. That's why the correct way to charge a system up without putting undue stress upon a compressor is to vacuum the whole system up and then load the refrigerant charge, all of this with the compressor off. That's what professional equipment is for. I prefer to pay a pro to have it done the right way rather than risk messing my system up.
Very well stated, I wish I had a like option for the forum. Maybe after the quarantine!
Re: 1990 Dodge D250 Cummins A/C Compressor
Posted: Sun Apr 19, 2020 5:24 pm
by bohica2xo
Yep. Charge liquid, straight in to the High side port with the engine STOPPED.
Get as much of the charge in to the evacuated system as you can before spinning that compressor. CLOSE the high side service valve BEFORE starting the engine.
Why the high side? Well, the check valves on a piston compressor will keep the liquid refrigerant from washing through the compressor & removing the oil.
This does not work on a scroll compressor. In the case of a scroll, pick the service port as far from the compressor as possible.
NEVER jumper out the cycling switch on a CCOT system. The compressor does not "suck in" refrigerant. Letting it short cycle while you add refrigerant is the best choice. Making it run continuously with very low suction will kill it.