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Nissan Sentra compressor question

hardbody on Sun November 04, 2012 1:46 PM User is offline

Year: 1990

Hello, so today I picked up an original compressor from a car at the junkyard, it is original as it has the R-12 sticker on it still. What I want to know is what do I need to do to make sure it is clean inside and ready for when I install it on my car that has been converted to 134? Thanks

Cussboy on Sun November 04, 2012 10:01 PM User is offline

Add some R134a type oil, turn the compressor by hand several times, drain that oil.


Repeat a third time.

Add the correct amount of R134a type oil; that's the best you can do.

hardbody on Sun November 04, 2012 11:44 PM User is offline

I was thinking of taking it apart and cleaning the inside real good, didn't know what would be good to use, can I use like brake clean or similar, than flush it out with the 134 oil?

HECAT on Mon November 05, 2012 1:02 PM User is offline

If it is a good clean usable salvage part; the oil flush only is recommended. It is not recommended to introduce solvents.

I would research more about the gasket, seal, and special tools availability and requirements before taking one apart.


HECAT: You support the Forum when you consider for your a/c parts.


hardbody on Mon November 05, 2012 1:21 PM User is offline

The compressor was sealed when I removed it from the car, the system had no pressure in it, no idea why, may have been a leak or broken line some where that I did not see. I've taken one of these a part before I just want to have the best chance of the compressor working when I install it. Thanks for the replies appreciate it.

hardbody on Mon November 05, 2012 1:22 PM User is offline

sorry, did not see an edit button so have to post again, where would the best place be to drain the oil from the compressor? Should I just remove the low pressure switch and drain it from there?

iceman2555 on Mon November 05, 2012 3:15 PM User is offlineView users profile

Not quite sure what compels you to take the compressor apart to 'clean' it. Several valid suggestions have been made to simply flush the unit and precede with the repair. The unit spec'd for this vehicle is a Calsonic NVR140S unit. A good flush (non solvent) should be adequate to remove all residual lubricants from the compressor. If there is no lube in the compressor, be very weary about the unit. If the unit was 'recycled' with 12 it should have mineral lube which would have kept the interior parts coated with a good mineral based oil coating. However, if the unit was 'recycled' with 134a there is a good chance that the internal parts are coated with a water absorbing material. Could the internals be rusted?
There are no special tools required for disassembly of the unit, remove clutch assembly and then remove the case bolts to gain access to the internal compressor parts. Suggest to complete the tear down over a suitable container. This will aid in capture of any migrating parts or those that fall out and are never seen again. A cookie sheet works great.
Suggest to take photos for re assembly. Clean the parts as necessary, inspect for rust, esp on valves, thrush washers and ALL bearing surfaces. Re lubricate, suggest to use mineral lube, reassemble the unit, install clutch assembly and insure correct air gap between the driver and pulley. Have trouble 'holding' some parts together....try a very light coating of Vaseline.....this may hold those parts in place to aid in reassemble. Remember, the term was very light coating.
However, if the system appears to be clean, then why not simply use a couple cans of PAG 46 lube to fill,rotate,drain---fill,rotate,drain the compressor. Then refill the compressor with the correct lubricant for the type refrigerant chosen.
Be aware this is a 'rotary vane' compressor and may not produce pressure spikes when it is rotated by hand. This lack of pressure may also be evident at start up. If this happens simply elevate the engine RPM (1200-1500 rpm) and turn the compressor on and off as rapidly as possible to 'break the vanes' loose. The vanes can become lodged with their housing and not free up until sufficient discharge pressure is produced to 'force' them out. The rapid cycling of the unit will utilize centrifugal force to break the 'hydraulic' hold of the lubricant to the vane and begin to produce adequate pressure to maintain correct operation. This is not a super common problem, but it does happen to this particular type of compressor. The system must be fully charged prior to this operation.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

hardbody on Mon November 05, 2012 6:42 PM User is offline

OK, spoke to a guy I know who was a master AC tech for many years (home and business AC), he also said not to take it apart , So I won't. I did remove the clutch down to the front of the compressor and cleaned all the parts, re-assembled and tested to make sure the clutch still worked, it did. He suggested using some R-11 to clean it out but I don't think the auto parts store would have it.

The unit was still in the car, it had the R-12 sticker on it so I'm assuming it is an original unit, no idea what type of freon was in the system before it made it's way to the junk yard.

When adding the oil to clean the inside as was specified, do I add the required amount (6.75oz.)? or add more just when flushing it out. Of course the proper amount would be added before installing.

Thanks for the replies

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