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2950 Air Conditioner

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Scott Kilby

10-10-2005 06:41:09

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After having my tractor a/c serviced from the dealer, it failed after a year and a half. Trying to save money, I replaced the expansion valve, dryer, and compressor myself. I had a mechanic come by the house and evacuate the system, and recharge. After putting the correct amount of 134a in the system and oil the gauges were around 0 on the low side and around 150 on the high side. Everything was looking like there was not enough coolant in the system. We added more 134a (one can) and the low side went to normal (20-30 psi), but the high side went to 450. We let about 1/2 a can out of the system, and it went back to where it was originally, (0 low, and 150 high). My mechanic said that he has never seen a system act like that. Do any of you know what the heck is going on? Everything on the system except the lines is less than one year old and the compressor, dryer, and exp. valve is new.

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Bob

10-10-2005 08:58:04

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Re: 2950 Air Conditioner in reply to Scott Kilby, 10-10-2005 06:41:09

You may have parts of the failed compressor jammed in the liquid line's quick-disconnect fitting.

The receiver-dryer has a dip-tube in it, and the body is marked "top" so the dryer gets oriented with the dip-tube at the bottom, so it is immersed in condensed refrigerant. Did you note that marking, and mount the dryer accordingly? If you did not, gas will be fed to the TXV, instead if liquid refrigerant, and the system will act as you describe. Post back and let us know what you find!

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Bob

10-10-2005 08:59:18

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Re: 2950 Air Conditioner in reply to Bob, 10-10-2005 08:58:04

P. S.....

Any chance you have the 2 lines switched at the compressor?

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Glen in TX

10-10-2005 08:00:17

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Re: 2950 Air Conditioner in reply to Scott Kilby, 10-10-2005 06:41:09

Did you flush lines, evaporator, & condensor well before installing new components? Old hoses can have stuff flake off inside and hose liners can collapse also. Those flakes will plug the expansion valve screen and compressor suction screen. Is the expansion valve and dryer on right? They are direction flow items and have to be installed right. It won't take much at all to plug the expansion valve. Sounds like it could be plugged up. That or something may have went wrong in compressor already too.

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Scott Kilby

10-11-2005 06:26:01

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Re: 2950 Air Conditioner in reply to Glen in TX, 10-10-2005 08:00:17

The system was flushed and the exp. valve and dryer were put on correctly. The only thing I can think of is the exp. valve must have gotten a small piece of something clogging it up. Is there any way of cleaning it without destroying? I did not include it in the system when I flushed, so it is a possibility that it is clogged. I appreciate all the responses and the help.

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Glen in TX

10-11-2005 14:03:38

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Re: 2950 Air Conditioner in reply to Scott Kilby, 10-11-2005 06:26:01

You should have had a cone shaped screen on inlet side of expansion valve. Many people take these out but it's really good to leave them in there. If there is no screen and something is stuck in there about all you can do is flush it back and forth with flush fluid and blow out lightly with air hoping you get it cleaned out. If you have a way to connect to expansion valve you can test it for flow by running some freon thru it. You can also test compressor if you have a test line setup for leaks or weak valves. What kind of compressor do have and from what source? I've always had better luck with the JD rebuilt or new compressors than the cheap auto supply ones. Many of the auto supply ones aren't completely rebuilt or may have a lighter duty clutch or not be exactly the same capacity compressor or have wrong pulleys on them. If you find stuff in expansion valve or in pump inlet screen consider flushing again or better yet replacing some hoses and lines. The lines inside the cab beam are bad about corroding causing problems and once those hoses or liners start flaking they need to be replaced or will just keep giving problems. Can use Ester oil for conversions but when PAG oil has been used a very thorough flushing job can still not work and hose replacements may be necessary. Some auto supplies and truck places may be able to make the hoses for less but not always. Also I believe the 50 series had that hi-pressure switch valve in top of cab and it could plug there too and too much 134A will shut the system down by it also.

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JDGnut

10-11-2005 15:17:45

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Re: 2950 Air Conditioner in reply to Glen in TX, 10-11-2005 14:03:38

Glen.. the 50 Series Row Crops had the pressure switchs.. the small utility tractors did not.. they just had gthe superheat switch on the back of the compressor.. and most of those are missing now... They do make a kit to install the high and low (refrig loss ) switches in the tractors.. this puts the switchs like the late 50/55 and up series row crop tractors had.. but this still doesn't fix the problem..
If the TXV is plugged, it will cause the low side pressure to be low-very low.. even a vacum.. and the high side pressure to be a just a little low... To check the expansion valve to see if it is working.. spray the sensing bulb with refrigerat... ( or the compressor air in a can will work.. just turn the can up side down and wit will spray out liquid.) This will freeze the TXV, and make it close.. watch the gauges while it closes.. if the pressure drops on the low side.. into a vacum at least the TXV is moving...

Also make sure your condensor is clean.. on the outside.. I'm guessing you measure the refrig by weight??? should be about 85-90% of the amount of R12 that went into the system... (by weight.)
Good Luck,
JDGnut

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Scott Kilby

10-13-2005 07:03:51

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Re: 2950 Air Conditioner in reply to JDGnut, 10-11-2005 15:17:45

JDGnut, that is exactly what is happening. The low side actually pulls a vacuum after a while and the high side is low as well. I will try the TXV test and get back with you on the results. I appreciate everyone's responses and help on this matter.

P.S. The condensor is sparkling clean, so I'm leaning toward the TXV now.

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Glen in TX

10-11-2005 21:54:02

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Re: 2950 Air Conditioner in reply to JDGnut, 10-11-2005 15:17:45

JDGnut, Glad someone stepped in keeping me out of trouble. :) I wasn't sure if this one had those switches or not? Scott, JD Publications or you local dealer may also have a copy of the (FOS) Fundamentals Of Service for Air Conditioning. Only one I see available now is the # FOS5708NC. The older FOS for AC are good to have too. It's just a good manual if doing more of your own AC work. For manuals call 1-800-522-7448 or visit their site or dealer can get them too. Good luck and let us know what you find out.

JD Tech Publications

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